Add the /manifest_template endpoint to return a string representation of the manifest template (#19367)

* return a string representation of the manifest template

* get rid of extra template

* add a comment

Author: brianjlai

airbyte-connector-builder-server/connector_builder/impl/default_api.py

@@ -13,7 +13,56 @@
 
 class DefaultApiImpl(DefaultApi):
     async def get_manifest_template(self) -> str:
-        return "Hello World"
+        return """version: "0.1.0"
+
+        definitions:
+          selector:
+            extractor:
+              field_pointer: []
+          requester:
+            url_base: "https://example.com"
+            http_method: "GET"
+            authenticator:
+              type: BearerAuthenticator
+              api_token: "{{ config['api_key'] }}"
+          retriever:
+            record_selector:
+              $ref: "*ref(definitions.selector)"
+            paginator:
+              type: NoPagination
+            requester:
+              $ref: "*ref(definitions.requester)"
+          base_stream:
+            retriever:
+              $ref: "*ref(definitions.retriever)"
+          customers_stream:
+            $ref: "*ref(definitions.base_stream)"
+            $options:
+              name: "customers"
+              primary_key: "id"
+              path: "/example"
+
+        streams:
+          - "*ref(definitions.customers_stream)"
+
+        check:
+          stream_names:
+            - "customers"
+
+        spec:
+          documentation_url: https://docsurl.com
+          connection_specification:
+            title: Source Name Spec # 'TODO: Replace this with the name of your source.'
+            type: object
+            required:
+              - api_key
+            additionalProperties: true
+            properties:
+              # 'TODO: This schema defines the configuration required for the source. This usually involves metadata such as database and/or authentication information.':
+              api_key:
+                type: string
+                description: API Key
+"""
 
     async def list_streams(self, streams_list_request_body: StreamsListRequestBody = Body(None, description="")) -> StreamsListRead:
         raise Exception("not yet implemented")