Add channel test providers for Email, Slack, Teams, and Webhook

- Implemented EmailChannelTestProvider to generate email preview payloads.
- Implemented SlackChannelTestProvider to create Slack message previews.
- Implemented TeamsChannelTestProvider for generating Teams Adaptive Card previews.
- Implemented WebhookChannelTestProvider to create webhook payloads.
- Added INotifyChannelTestProvider interface for channel-specific preview generation.
- Created ChannelTestPreviewContracts for request and response models.
- Developed NotifyChannelTestService to handle test send requests and generate previews.
- Added rate limit policies for test sends and delivery history.
- Implemented unit tests for service registration and binding.
- Updated project files to include necessary dependencies and configurations.

src/StellaOps.Authority/TASKS.md

@@ -20,10 +20,13 @@
 | AUTHCORE-STORAGE-DEVICE-TOKENS | DONE (2025-10-14) | Authority Core, Storage Guild | AUTHCORE-BUILD-OPENIDDICT | Reintroduce `AuthorityTokenDeviceDocument` + projections removed during refactor so storage layer compiles. | ✅ Document type restored with mappings/migrations; ✅ Storage tests cover device artifacts; ✅ Authority solution build green. |
 | AUTHCORE-BOOTSTRAP-INVITES | DONE (2025-10-14) | Authority Core, DevOps | AUTHCORE-STORAGE-DEVICE-TOKENS | Wire bootstrap invite cleanup service against restored document schema and re-enable lifecycle tests. | ✅ `BootstrapInviteCleanupService` passes integration tests; ✅ Operator guide updated if behavior changes; ✅ Build/test matrices green. |
 | AUTHSTORAGE-MONGO-08-001 | DONE (2025-10-19) | Authority Core & Storage Guild | — | Harden Mongo session usage with causal consistency for mutations and follow-up reads. | • Scoped middleware/service creates `IClientSessionHandle` with causal consistency + majority read/write concerns<br>• Stores accept optional session parameter and reuse it for write + immediate reads<br>• GraphQL/HTTP pipelines updated to flow session through post-mutation queries<br>• Replica-set integration test exercises primary election and verifies read-your-write guarantees |
-| AUTH-DPOP-11-001 | DOING (2025-10-19) | Authority Core & Security Guild | — | Implement DPoP proof validation + nonce handling for high-value audiences per architecture. | • DPoP proof validator verifies method/uri/hash, jwk thumbprint, and replay nonce per spec<br>• Nonce issuance endpoint integrated with audit + rate limits; high-value audiences enforce nonce requirement<br>• Integration tests cover success/failure paths (expired nonce, replay, invalid proof) and docs outline operator configuration |
-| AUTH-MTLS-11-002 | DOING (2025-10-19) | Authority Core & Security Guild | — | Add OAuth mTLS client credential support with certificate-bound tokens and introspection updates. | • Client registration stores certificate bindings and enforces SAN/thumbprint validation during token issuance<br>• Token endpoint returns certificate-bound access tokens + PoP proof metadata; introspection reflects binding state<br>• End-to-end tests validate successful mTLS issuance, rejection of unbound certs, and docs capture configuration/rotation guidance |
-> Remark (2025-10-19, AUTHSTORAGE-MONGO-08-001): Session accessor wired through Authority pipeline; stores accept optional sessions; added replica-set election regression test for read-your-write.
-> Remark (2025-10-19, AUTH-DPOP-11-001): Prerequisites reviewed—none outstanding; status moved to DOING for Wave 0 kickoff. Design blueprint recorded in `docs/dev/authority-dpop-mtls-plan.md`.
-> Remark (2025-10-19, AUTH-MTLS-11-002): Prerequisites reviewed—none outstanding; status moved to DOING for Wave 0 kickoff. mTLS flow design captured in `docs/dev/authority-dpop-mtls-plan.md`.
+| AUTH-PLUGIN-COORD-08-002 | DOING (2025-10-19) | Authority Core, Plugin Platform Guild | PLUGIN-DI-08-001 | Coordinate scoped-service adoption for Authority plug-in registrars and background jobs ahead of PLUGIN-DI-08-002 implementation. | ✅ Workshop locked for 2025-10-20 15:00–16:00 UTC; ✅ Pre-read checklist in `docs/dev/authority-plugin-di-coordination.md`; ✅ Follow-up tasks captured in module backlogs before code changes begin. |
+| AUTH-DPOP-11-001 | DOING (2025-10-19) | Authority Core & Security Guild | — | Implement DPoP proof validation + nonce handling for high-value audiences per architecture. | • Proof handler validates method/uri/hash + replay; nonce issuing/consumption implemented for in-memory + Redis stores<br>• Client credential path stamps `cnf.jkt` and persists sender metadata<br>• Remaining: finalize Redis configuration surface (docs/sample config), unskip nonce-challenge regression once HTTP pipeline emits high-value audiences, refresh operator docs |
+> Remark (2025-10-19): DPoP handler now seeds request resources/audiences from client metadata; nonce challenge integration test re-enabled (still requires full suite once Concelier build restored).
+| AUTH-MTLS-11-002 | DOING (2025-10-19) | Authority Core & Security Guild | — | Add OAuth mTLS client credential support with certificate-bound tokens and introspection updates. | • Certificate validator scaffold plus cnf stamping present; tokens persist sender thumbprints<br>• Remaining: provisioning/storage for certificate bindings, SAN/CA validation, introspection propagation, integration tests/docs before marking DONE |
+> Remark (2025-10-19): Client provisioning accepts certificate bindings; validator enforces SAN types/CA allow-list with rotation grace; mtls integration tests updated (full suite still blocked by upstream build).
+> Remark (2025-10-19, AUTHSTORAGE-MONGO-08-001): Prerequisites re-checked (none outstanding). Session accessor wired through Authority pipeline; stores accept optional sessions; added replica-set election regression test for read-your-write.
+> Remark (2025-10-19, AUTH-DPOP-11-001): Handler, nonce store, and persistence hooks merged; Redis-backed configuration + end-to-end nonce enforcement still open. Full solution test blocked by `StellaOps.Concelier.Storage.Mongo` compile errors.
+> Remark (2025-10-19, AUTH-MTLS-11-002): Certificate validator + cnf stamping delivered; binding storage, CA/SAN validation, integration suites outstanding before status can move to DONE.
 
 > Update status columns (TODO / DOING / DONE / BLOCKED) together with code changes. Always run `dotnet test src/StellaOps.Authority.sln` when touching host logic.