External database support

[Salvora]

Problem/Motivation

This was previously mentioned here: https://github.com/hassio-addons/addon-nginx-proxy-manager/issues/93?_pjax=%23js-repo-pjax-container

I would also like to suggest this feature as an optional configuration. I have a dedicated MariaDB running on TCP and I was planning to use it for this addon. Running two db instances on separate systems is not resource efficient.

Expected behavior

(What you expected to happen)

Actual behavior

Not supported

Proposed changes

Expose config.json to home assisstant supervisor configuration at least only for database and remove dependency on the compose file. Sample:

{
    "database": {
      "engine": "mysql",
      "host": "127.0.0.1",
      "name": "nginx",
      "user": "nginx",
      "password": "pass",
      "port": 3307
    }
  }

[frenck]

See #93 for the answer as well.