Add option for using docker volume for data persistence

[m-danya]

Motivation

Current docs provide two types of using Fief in projects:

1. Local setup: single docker container
2. Production setup with reverse proxy and SSL setup

I think it will be useful to add --use-docker-volume option to quickstart command to provide complete command for local setup with persistence. Currently, the data is stored inside the container without using volumes, and while it technically will persist across container restart, using volume is more reliable way to persist data (e.g. across rebuilding Fief image).

I believe persistence can be useful in local setup.

Docs improvements

If this PR will be accepted, the docs also should be edited to highlight this option. In fact, the docs now contain a bit of misleading information, as current setup doesn't persist data during container rebuilds:

If you need to restart or recreate your container, you'll need to set the same secrets again.

Also, the default value for DATABASE_LOCATION in https://docs.fief.dev/self-hosting/environment-variables/ is stated is "Current working directory", while it's actually /data/db for Docker setup

[frankie567]

That's a super helpful suggestion, @m-danya, thanks 🙏 I'm even thinking it should be True by default. What do you think?

[m-danya]

@frankie567 Hi, thanks! Yes, that seems reasonable to me.

[m-danya]

The mypy check fails with this:

cmd [3] | mypy fief/
fief/dependencies/fief.py:18: error: Item "None" of "Coroutine[Any, Any, Any] | None" has no attribute "cr_frame"  [union-attr]

Since I'm not in the context of what's going on in this file, could you please fix the tests? I've got "Allowing edits by maintainers" checked on this pull request.