modules.zitadel: support generic OIDC IdPs
idps.<name>.type = "oidc" with an issuer, a literal clientId as
alternative to clientIdFile, a display name independent of the attribute
name and per-IdP providerOptions (default unchanged: linking, creation and
auto update allowed). Generic OIDC IdPs use PKCE and ID token mapping.
Zitadel 2.71 does not fetch the issuer's discovery document when the IdP
is created, only at login, so the reconciler needs no ordering on the
provider.