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.
if chatwoot receives an email of already existing contact with a different case say "Care@example.com", before this fix, it will throw an error. Now it will retrieve existing contact
Fixes: #2553
Co-authored-by: Sojan Jose <sojan@pepalo.com>
