# 2025-10-20 — Authority Identity Provider Registry & DPoP nonce updates

## Summary
- Authority host now resolves identity providers through the new metadata/handle pattern introduced in `StellaOps.Authority.Plugins.Abstractions`. Runtime handlers (`ValidateClientCredentialsHandler`, `ValidatePasswordGrantHandler`, `ValidateAccessTokenHandler`, bootstrap endpoints) acquire providers with `IAuthorityIdentityProviderRegistry.AcquireAsync` and rely on metadata (`AuthorityIdentityProviderMetadata`) for capability checks.
- Unit and integration tests build lightweight `ServiceProvider` instances with test plugins, matching production DI behaviour and ensuring the new registry contract is exercised.
- DPoP nonce enforcement now prefers `NormalizedAudiences` when populated and gracefully falls back to the configured `RequiredAudiences`, eliminating the runtime type mismatch that previously surfaced during test runs.

## Operator impact
- No configuration changes are required; existing YAML and environment-based settings continue to function.
- Documentation examples referencing password/mTLS bootstrap flows remain accurate. The new registry logic simply ensures providers advertised in configuration are resolved deterministically and capability-gated before use.

## Developer notes
- When adding new identity providers or tests, register plugins via `ServiceCollection` and call `new AuthorityIdentityProviderRegistry(serviceProvider, logger)`.
- For DPoP-required endpoints, populate `security.senderConstraints.dpop.nonce.requiredAudiences` or rely on defaults; both now funnel through the normalized set.