Fix: Make swagger doc compliant to OpenAPI (#3394)

This fixes issues in the swagger.json file. The motivation to do so is to be able to generate API clients using https://openapi-generator.tech Doing so will require further changes to the api spec, but this seems like a good first step since it is now "valid" according to editor.swagger.io and openapi-generator validate.

Fixes #2806

swagger/paths/application/inboxes/update.yml

@@ -16,17 +16,18 @@ patch:
       required: true
       schema:
         type: object
+        required:
+          - enable_auto_assignment
         properties:
           name:
             type: string
             description: The name of the inbox
           enable_auto_assignment:
             type: boolean
-            required: true
             description: 'Enable Auto Assignment'
           avatar:
-            type: file
-            required: false
+            type: string
+            format: binary
             description: 'Image file for avatar'
           channel:
             type: object