Add option to disable Gravatar via environment variable (Privacy improvement)

[rezzorix]

Related to #1843

This adds an optional environment variable, DISABLE_GRAVATAR, to disable Gravatar usage.
It is useful for users who want to improve privacy and avoid external requests to Gravatar.

Add to docker-compose.yml

environment:
  DISABLE_GRAVATAR: 'true'

When set to true:

• Gravatar is no longer queried when disabled.
• Gravatar URLs are not generated
• the avatar field returns an empty string
• the frontend falls back to the default local avatar

When set to false or left unset:

• existing behavior remains unchanged / Gravatar is requested (again)

Tested with:

• new users
• existing users

[nginxproxymanagerci]

Docker Image for build 1 is available on DockerHub:

nginxproxymanager/nginx-proxy-manager-dev:pr-5470

Note

Ensure you backup your NPM instance before testing this image! Especially if there are database changes.
This is a different docker image namespace than the official image.

Warning

Changes and additions to DNS Providers require verification by at least 2 members of the community!