docs: schema update for activitypub acp route

public/openapi/read.yaml

@@ -92,6 +92,8 @@ paths:
     $ref: 'read/admin/settings/user.yaml'
   /api/admin/settings/post:
     $ref: 'read/admin/settings/post.yaml'
+  /api/admin/settings/activitypub:
+    $ref: 'read/admin/settings/activitypub.yaml'
   /api/admin/settings/advanced:
     $ref: 'read/admin/settings/advanced.yaml'
   /api/admin/manage/categories:

public/openapi/read/admin/settings/activitypub.yaml

@@ -0,0 +1,19 @@
+get:
+  tags:
+    - admin
+  summary: Get federation (ActivityPub) settings
+  responses:
+    "200":
+      description: ""
+      content:
+        application/json:
+          schema:
+            allOf:
+              - type: object
+                properties:
+                  title:
+                    type: string
+                  instanceCount:
+                    type: number
+                    description: The number of ActivityPub-enabled instances that this forum knows about.
+              - $ref: ../../../components/schemas/CommonProps.yaml#/CommonProps