Support the file:// syntax for AUTHENTIK_BOOTSTRAP_PASSWORD

[Schabimperle]

Is your feature request related to a problem? Please describe. I would like to use a docker secret for the AUTHENTIK_BOOTSTRAP_PASSWORD environment variable. As described at the configuration page it is possible to load some variables from files using the file:// syntax, e.g. for AUTHENTIK_SECRET_KEY. However, this doesn't work for BOOTSTRAP environment variables.

Describe the solution you'd like I guess it should be possible to use the same approach for BOOTSTRAP environment variables as for the other ones to support the file:// syntax.