Authelia: Support protection of multiple root domains

[lued]

I'm looking to redirect another domain through Authelia that is not a subdomain of the protected domain.

I guess I'm more or less looking for the correct field for session/domain configuration. Comments say "If empty, the cookie is restricted to the subdomain of the issuer", although this is a required field. I couldn't find anything in the documentation regarding this type of configuration.

authelia/configuration.yml
```access_control:
default_policy: deny

rules:
- domain: '*.{domain 1}'
policy: two_factor

- domain: '*.{domain 2}'
  policy: two_factor

...
...

session:
...

# The domain to protect.
# Note: the authenticator must also be in that domain. If empty, the cookie
# is restricted to the subdomain of the issuer.
domain: {domain 1 as a required field}
```

Kind regards

[nightah]

This isn't possible today, the cookie and all the respective configuration is tied to a single root domain.
You would need to run multiple instances of Authelia to achieve your intended outcome.

Though this is something that the team should discuss and design to support in future. I think a single instance of Authelia with the ability to support multiple domains is something that we should consider, as the topic is gaining a lot of traction and interest.

cc @clems4ever @james-d-elliott

[james-d-elliott]

I'm wondering if we could use OIDC plus a container that just does the OIDC handshake with Authelia.

[dginhoux]

I use multiple domains, with on instance per domain.

Everything work fine. But if I use ldap as user backend, the same for all domains but for authelia, can I use the same storage backend (myssl, same database) for all domains instanced...?