Adapt the data and auth provider to be Solid compliant

When we will have [completed Solid-OIDC implementation](https://github.com/assemblee-virtuelle/activitypods/issues/229), we will need to adapt the data provider and the auth provider.

In particular, we should allow to connect with a WebID, like other Solid client libraries do. We should still allow to select a Pod provider from a list, like we do on ActivityPods.

We should test the provider with "regular" Solid pods.

> Idea coming from a discussion with @lecoqlibre, which also interested people from Logilab

Start with the linked Solid-OIDC implementation issue, then inspect the existing data and auth providers and how ActivityPods selects a Pod provider. Validate WebID connection and provider-list selection against regular Solid pods; done means both providers work with those flows.

Written by the indexing model from the issue text.