* refactor!: refactor OAuth client authorization api
`OAuthState::start_authorization` now accepts a declarative `AuthorizationRequest`
describing the client's available identity material and selects the highest-priority
mechanism the server supports: pre-registered client information → Client ID
Metadata Documents (SEP-991) → Dynamic Client Registration.
This replaces the three mechanism-specific entry points (`start_authorization`,
`start_authorization_with_metadata_url`, `start_authorization_with_preregistered_client`),
where callers previously had to know which mechanism to pick. `AuthorizationSession::new`
is consolidated the same way, and the failure-recovery pattern from #994 (returning the
manager alongside the error so `OAuthState` recovers to `Unauthorized` on transient failures)
is now applied across all registration paths. Includes new `RecordingOAuthHttpClient`-based
tests covering the priority matrix and recovery semantics, plus updated docs, examples, and
conformance client.
* fix: dcr registration uses requested application type
* fix: error for invalid combination
e903341136