@ mention of reviewers`

@Didayolo @ihsaan-ullah`

A brief description of the purpose of the changes contained in this PR.

This should fix the problem of persistent certificates on caddy:

I changed the caddy image to the official one, upgrading it to version 2.7.6 (the one we were using was an unofficial 1.0.3)
I updated the syntax of the Caddyfile to support the changes caddy v2 brings
Changed the volumes in the docker-compose.yml for the container to use the recommended ones from caddy's Docker Hub
- Added ./caddy_data:/data which is used by the image to store important information, certificates included.
- Added ./caddy_config:/config which is used by the image to store some configuration (I'm not sure if it's really needed in our case)
- Renamed ./Caddyfile:/etc/Caddyfile to ./Caddyfile:/etc/caddy/Caddyfile (new official location for the Caddyfile)
- Removed ./certs/caddy:/etc/caddycerts which is not present on the official Docker Hub