Add basic dynamic configuration with volume labels

[rdelaage]

closes #256

This PR add a basic docker discovery system to autorestic. Autorestic can now connect to a docker daemon, check for volumes with a autorestic.enable set to 1 or true and backup to the backend configured in autorestic.to label. You can also specify a cron in autorestic.cron label.

This service discovery is only enabled when the --docker-discovery flag is set.

Since I am used to work with podman and autorestic use the docker command, I needed to add a --docker-host flag used to change the host used in the docker command if specified (unix:///var/run/user/1000/podman/podman.sock for me when working with the podman user socket)

The app still need a static configuration file to configure backends and global options. You can also use location both in the static configuration file and docker labels. The new behavior just append the dynamic configuration to the config variable after parsing the config file.

This PR is in draft mode because I would like your suggestions about this feature.

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Name	Status	Preview	Updated
autorestic	✅ Ready (Inspect)	Visit Preview	Nov 14, 2022 at 2:56PM (UTC)

[rdelaage]

I added all the relevant options for the volume type. The list of backend is ; separated. You can specify a copy option with autorestic.copy.<fromRepo> and a ; separated list of backend. The forget option with autorestic.forget, the hooks with autorestic.hooks.dir, autorestic.hooks.before, autorestic.hooks.after, autorestic.hooks.success, autorestic.hooks.failure and finally additional flags with autorestic.options.<command|all>.<flagName> and a ; separated list of values.

[Akruidenberg]

Any progres?

[rdelaage]

Hello @Akruidenberg I was supposed to do some refactoring first but I didn't found time, I am quite busy right now in my personal life. But feel free to test it and suggest things!