feat: update openapi spec with identity and is_anonymous fields (#1573)

## What kind of change does this PR introduce?

Adds the `Identity` and `is_anonymous` fields to OpenAPI spec. This is
so we can use the `openapi.yml` as a sgeneral reference from which to
generate Hook Payloads, which contain `User` objects.

Identity Fields taken from the [identity
model](https://github.com/supabase/auth/blob/master/internal/api/identity.go)

## More Context

User objects are generated by:

1. Converting the `openapi.yml` into JSONSchema. Currently this is done
via OpenAI though a modified version of [a yml to jsonschema converter
should work with modifications as
well](https://www.npmjs.com/package/yaml-to-json-schema). We don't use
the latter as there's an additional step of converting the output
jsonschema into a format that JSON Faker can accept (adding the
JSONSchema version etc)
2. Using [JSONSchema to generate a fake
payload](https://json-schema-faker.js.org/)

## Use

The plan is to embed the JSONSchema into each Hook example so developers
can copy paste into JSONSchema Faker or similar tool to generate a fake
payload.

openapi.yaml

@@ -1840,7 +1840,7 @@ components:
         identities:
           type: array
           items:
-            type: object
+            $ref: "#/components/schemas/IdentitySchema"
         banned_until:
           type: string
           format: date-time
@@ -1853,6 +1853,8 @@ components:
         deleted_at:
           type: string
           format: date-time
+        is_anonymous:
+          type: boolean
 
     SAMLAttributeMappingSchema:
       type: object
@@ -1958,6 +1960,35 @@ components:
             Usually one of:
             - totp
 
+    IdentitySchema:
+      type: object
+      properties:
+        identity_id:
+          type: string
+          format: uuid
+        id:
+          type: string
+          format: uuid
+        user_id:
+          type: string
+          format: uuid
+        identity_data:
+          type: object
+        provider:
+          type: string
+        last_sign_in_at:
+          type: string
+          format: date-time
+        created_at:
+          type: string
+          format: date-time
+        updated_at:
+          type: string
+          format: date-time
+        email:
+          type: string
+          format: email
+
   responses:
     OAuthCallbackRedirectResponse:
       description: >