Provide default OIDC static tenant resolver

[sberyozkin]

Description

A typical case, when more than one social provider is configured in application.properties, is to start a login process with the last path segment containing the tenant name, for example, given these 2 tenant declarations:

quarkus.oidc.google.provider=google
quarkus.oidc.google.client-id=...
quarkus.oidc.google.credentials.secret=..

quarkus.oidc.github.provider=github
quarkus.oidc.github.client-id=...
quarkus.oidc.github.credentials.secret=..

The UI will offer Google and GitHub login options with URLs like /service/login/google, /service/login/github, etc, giving Quarkus a hint which social provider to use.

However, right now, a user has to register a custom TenantResolver which will just get the last path segment from the request path, and use it as a value of the tenant id, and then when the authenticated user returns accessing some application URL, a tenant id property can be checked in RequestContext since the tenant id is encoded in the session cookie. It is a fairly typical, boilerplate code.

It would be useful to provide such a logic by default if no custom TenantResolver is available.

Implementation ideas

If non-default OIDC tenants are configured but no TenantResolver is registered, provide a default resolution logic which will 1) check RoutingContext tenantId attribute - if it exists - the user is already authenticated, return it 2) otherwise get the last path segment and offer it as a tenant id.

[quarkus-bot]

/cc @pedroigor (oidc)