Chore: API Improvements (#2956)

- API to fetch info of a single inbox
- Document passing custom_attributes in the API
- Ability to filter contacts with contact identifier in search API

swagger/paths/contact_inboxes/create.yml

@@ -5,6 +5,12 @@ post:
   description: Create a contact inbox record for an inbox
   summary: Create contact inbox
   parameters:
+    - $ref: '#/parameters/account_id'
+    - name: id
+      in: path
+      type: number
+      description: ID of the contact
+      required: true
     - name: data
       in: body
       required: true