Document and test the Firebase Auth metadata timestamp mapping

Author: jskeet

docs/mapping.md

@@ -184,7 +184,14 @@ TBD: Where the `app-id` part comes from.
 
 The `subject` attribute of the CloudEvent is of the form `users/{uid}` where the
 `uid` value is taken from the `uid` property within the original
-`data` property. (This value is still populated within the CloudEvent data as well.)
+`data` property. This value is still retained within the CloudEvent data as well.
+
+Additionally, two properties within the CloudEvent have different names
+to those in the GCF HTTP event. Within the `metadata` top-level
+property, there are two timestamps. In GCF HTTP events these have
+names of `createdAt` and `lastSignedInAt`; in the CloudEvent
+representation the names are `createTime` and `lastSignInTime`
+respectively.
 
 ### Firestore document events (tentative)
 

events/events_data.go

@@ -9,7 +9,8 @@
   "data": {
     "email": "[email protected]",
     "metadata": {
-      "createdAt": "2020-05-26T10:42:27Z"
+      "createTime": "2020-05-26T10:42:27Z",
+      "lastSignInTime": "2020-10-24T11:00:00Z"
     },
     "providerData": [
       {

events/generate/data/firebase-auth-cloudevent-input.json

@@ -9,7 +9,8 @@
   "data": {
     "email": "[email protected]",
     "metadata": {
-      "createdAt": "2020-05-26T10:42:27Z"
+      "createTime": "2020-05-26T10:42:27Z",
+      "lastSignInTime": "2020-10-24T11:00:00Z"
     },
     "providerData": [
       {

events/generate/data/firebase-auth-cloudevent-output.json

@@ -2,7 +2,8 @@
   "data": {
     "email": "[email protected]",
     "metadata": {
-      "createdAt": "2020-05-26T10:42:27Z"
+      "createdAt": "2020-05-26T10:42:27Z",
+      "lastSignedInAt": "2020-10-24T11:00:00Z"
     },
     "providerData": [
       {

events/generate/data/firebase-auth-legacy-input.json

@@ -2,7 +2,8 @@
   "data": {
     "email": "[email protected]",
     "metadata": {
-      "createdAt": "2020-05-26T10:42:27Z"
+      "createdAt": "2020-05-26T10:42:27Z",
+      "lastSignedInAt": "2020-10-24T11:00:00Z"
     },
     "providerData": [
       {