[Feature Request] Improve security by using docker secret for password

Please support "docker secrets" for passwords. Most major apps (and all databases) support this.

So instead of this:

version: "3.7"
services:

  postgresql:
    environment:
      POSTGRES_PASSWORD: foo
    # ...

  odoo:
    environment:
      PASSWORD: foo

We can do this:

version: "3.7"
services:

  postgresql:
    secrets:
      - postgresql_password
    environment:
      POSTGRES_PASSWORD_FILE: /run/secrets/odoo_postgresql_password     # supported
    # ...

  odoo:
    secrets:
      - postgresql_password
    environment:
      PASSWORD_FILE: /run/secrets/odoo_postgresql_password              # unsupported

  secrets:
    postgresql_password:
      file: odoo_postgresql_password

This is more secure. Most secure database deployments do it like this, so odoo is the weak link in the chain (as we need to put the password in plaintext).

Here are the docs.

Start with the Docker Compose secrets configuration reference linked in the issue and compare its PostgreSQL example with the Odoo service example. Trace how the Odoo container currently receives its password, then define the supported secret-file behavior and verify that passwords can be supplied without plaintext environment values.