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.
* [#247] Filters conversation by status
* Fixes conversation finder specs
* [#248] Paginates conversation
* Use method name in description
* Move page to default param, add filters on frontend
* Fix code climate issues