RFC Updates

- Added sample files detail usage of the @CacheControl and @onDelete directives
- Added section to the RFC to specifically talk about the 2 new directives
- Added section to RFC about removing the SQLite.swift third party dependency

Author: BobaFetters

apollo-ios/Design/Samples/cache-control-samples.md

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+# `@cacheControl` Examples
+
+## Scalar Samples
+
+For scalar types, fields should always inherit from their parent type. However, you can override the parent value at the field level for individual fields. 
+
+### Example 1
+
+In this example, `@cacheControl` is applied to the `Author` type. All fields within the `Author` type are scalars, so they will automatically inherit the max age of 3600 from the `Author` type.
+
+```graphql
+type Author `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int!
+}
+```
+
+### Example 2
+
+In this example, `@cacheControl` is applied to the `Author` type. All fields within the `Author` type are scalars, so they will automatically inherit the max age of 3600 from the `Author` type. However, the `bookCount` field overrides this and gets a `maxAge` of 300.
+
+```graphql
+type Author `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int! `@cacheControl`(maxAge: 300)
+}
+```
+
+### Example 3
+
+In this example only the `bookCount` field has a `maxAge` applied, the `Author` type and all other fields within the type will receive the default max age value.
+
+```graphql
+type Author {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int! `@cacheControl`(maxAge: 300)
+}
+```
+
+## Composite Type Examples
+
+### Example 1
+
+In this example the `author` field on `Book` has a `maxAge` of 3600 which is set on the `Author` type.
+
+```graphql
+type Author `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int!
+}
+
+type Book {
+  id: ID!
+  title: String!
+  author: Author! # This field uses the max age from the Author type above
+}
+```
+
+### Example 2
+
+In this example the `Author` type has a `maxAge` of 3600, however the `author` field on `Book` overrides this with a `maxAge` of 600.
+
+```graphql
+type Author `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int!
+}
+
+type Book {
+  id: ID!
+  title: String!
+  author: Author! `@cacheControl`(maxAge: 600)
+}
+```
+
+### Example 3
+
+In this example no `maxAge` is set for the `Author` type, the `author` field on `Book` is setting its `maxAge` to 600.
+
+```graphql
+type Author {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int!
+}
+
+type Book {
+  id: ID!
+  title: String!
+  author: Author! `@cacheControl`(maxAge: 600)
+}
+```
+
+### Example 4
+
+In this example there is no `maxAge` set on the `Author` type so it would have a default `maxAge` of 0. It does not automatically inherit from the `Book` type.
+
+```graphql
+type Author {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int!
+}
+
+type Book `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  title: String!
+  author: Author!
+}
+```
+
+### Example 5
+
+In this example the `inheritMaxAge` is used on the `author` field of the `Book` type so that it inherits the `maxAge` of `Book` instead of using the value set on the `Author` type.
+
+```graphql
+type Author `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int!
+}
+
+type Book `@cacheControl`(maxAge: 1800) {
+  id: ID!
+  title: String!
+  author: Author! `@cacheControl`(inheritMaxAge: true) #uses 1800 instead of 3600
+}
+```
+
+### Example 6
+
+In this example `inheritMaxAge` is applied to the `Author` type, so by default it has a `maxAge` of 0, but since `Book` has a `maxAge` of 1800 that is inherited by the `Author` type.
+
+```graphql
+type Author `@cacheControl`(inheritMaxAge: true) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int!
+}
+
+type Book `@cacheControl`(maxAge: 1800) {
+  id: ID!
+  title: String!
+  author: Author! # uses 1800 because of inheritMaxAge on Author
+}
+```
+
+## Operation Override Examples
+
+Example 1
+
+This example shows how you can override `maxAge` values at the operation level.
+
+```
+# Schema
+
+type Query {
+  authors: [Author!]!
+}
+
+type Author `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int!
+  books: [Book!]!
+}
+
+type Book {
+  id: ID!
+}
+
+# Operations
+
+query GetAuthorsWithBooks {
+  authors { # 3600 - Because it's of type Author which has maxAge 3600
+    id # 3600 - Because it's a scalar so inherits its parent field's maxAge
+    bookCount `@cacheControl`(maxAge: 60) # 60 - Because it's overridden here in the operationSample
+    books { # 0 - Default value, because no maxAge specified on Book
+            # and it's not scalar so doesn't inherit its parent's maxAge
+      id # 0 - Because it's a scalar so inherits its parent field's maxAge
+    }
+  }
+}
+```
+
+## Schema and Operation Examples
+
+### Example 1
+
+```graphql
+# Schema
+
+type Query {
+  authors: [Author!]!
+}
+
+type Author `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int! `@cacheControl`(maxAge: 60)
+  books: [Book!]!
+}
+
+type Book {
+  id: ID!
+}
+
+# Operations
+
+query GetAuthorsWithBooks {
+  authors { # 3600 - Because it's of type Author which has maxAge 3600
+    id # 3600 - Because it's a scalar so inherits its parent field's maxAge
+    bookCount # 60 - Because it's specified on Author.bookCount
+    books { # 0 - Default value, because no maxAge specified on Book
+            # and it's not scalar so doesn't inherit its parent's maxAge
+      id # 0 - Because it's a scalar so inherits its parent field's maxAge
+    }
+  }
+}
+```
+
+### Example 2
+
+```graphql
+# Schema
+
+type Query {
+  authors: [Author!]!
+}
+
+type Author `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int! `@cacheControl`(maxAge: 60)
+  books: [Book!]!
+}
+
+type Book `@cacheControl`(maxAge: 1800) {
+  id: ID!
+}
+
+# Operations
+
+query GetAuthorsWithBooks {
+  authors { # 3600 - Because it's of type Author which has maxAge 3600
+    id # 3600 - Because it's a scalar so inherits its parent field's maxAge
+    bookCount # 60 - Because it's specified on Author.bookCount
+    books { # 1800 - Because it is specified on the Book type
+      id # 1800 - Because it's a scalar so inherits its parent field's maxAge
+    }
+  }
+}
+```
+
+### Example 3
+
+```graphql
+# Schema
+
+type Query {
+  authors: [Author!]!
+}
+
+type Author `@cacheControl`(maxAge: 3600) {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  bookCount: Int! `@cacheControl`(maxAge: 60)
+  books: [Book!]! `@cacheControl`(maxAge: 900)
+}
+
+type Book `@cacheControl`(maxAge: 1800) {
+  id: ID!
+}
+
+# Operations
+
+query GetAuthorsWithBooks {
+  authors { # 3600 - Because it's of type Author which has maxAge 3600
+    id # 3600 - Because it's a scalar so inherits its parent field's maxAge
+    bookCount # 60 - Because it's specified on Author.bookCount
+    books { # 900 - Because Author.books is overriding the maxAge specified on the Book type
+      id # 900 - Because it's a scalar so inherits its parent field's maxAge
+    }
+  }
+}
+```
+
+### Example with an interface
+
+```graphql
+# Schema
+
+type Query {
+  auth: Auth
+}
+
+interface Sensitive `@cacheControl`(maxAge: 5) {
+  id: ID!
+}
+
+type Auth implements Sensitive {
+  id: ID!
+  password: String
+}
+
+# Operations
+
+query GetAuthorsWithBooks {
+  auth { # 5 - Because it's of type Author which implements Sensitive which
+         # has maxAge 5
+    password # 5 - Because it's a scalar so inherits its parent field's maxAge
+  }
+}
+```

apollo-ios/Design/Samples/on-delete-samples.md

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+# `@onDelete` Examples
+
+## Example 1
+
+In this example, the `book` field referenced by the `Author` type is not deleted from the cache when the `Author` is deleted. This is because by default, composite types aren't deleted from the cache when an object that references them is deleted. Only scalar fields are deleted by default.
+
+```graphql
+type Author {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  book: Book!
+}
+
+type Book {
+  id: ID!
+  title: String!
+}
+```
+
+## Example 2
+
+In this example, the `@onDelete` directive is used on the `book` field to say that the `Book` object associated with the `Author` should be deleted from the cache whenever the `Author` is deleted.
+
+```graphql
+type Author {
+  id: ID!
+  firstName: String!
+  lastName: String!
+  book: Book! @onDelete(cascade: true)
+}
+
+type Book {
+  id: ID!
+  title: String!
+}
+```