MySQL socket and variables in docker-compose

Hi,

  1. Is any option to use MySQL socket, not host and port. socketPath or something like that?

  2. On the official docker hub (Docker Hub) is docker-compose example.

environment:
      # see https://ghost.org/docs/config/#configuration-options
      database__client: mysql
      database__connection__host: db
      database__connection__user: root
      database__connection__password: example
      database__connection__database: ghost

can i use different variable in the same way?
example:

      mail__transport: SMTP
      mail__options__serwice: Mailgun
      ...
      admin__url: https://topsecret.domain.com

can i use all config options in that way?