fixes: #3853
- Introduced DISABLE_GRAVATAR Global Config, which will stop chatwoot from making API requests to gravatar
- Cleaned up avatar-related logic and centralized it into the avatarable concern
- Added specs for the missing cases
- Added migration for existing installations to move the avatar to attachment, rather than making the API that results in 404.
- fix the wrong conversation status being sent in webhooks
- additional information in websocket events
- refactor activity messaging code
- move activity message generation to background job to stop the callback loop
