Add Authority Advisory AI and API Lifecycle Configuration

- Introduced AuthorityAdvisoryAiOptions and related classes for managing advisory AI configurations, including remote inference options and tenant-specific settings.
- Added AuthorityApiLifecycleOptions to control API lifecycle settings, including legacy OAuth endpoint configurations.
- Implemented validation and normalization methods for both advisory AI and API lifecycle options to ensure proper configuration.
- Created AuthorityNotificationsOptions and its related classes for managing notification settings, including ack tokens, webhooks, and escalation options.
- Developed IssuerDirectoryClient and related models for interacting with the issuer directory service, including caching mechanisms and HTTP client configurations.
- Added support for dependency injection through ServiceCollectionExtensions for the Issuer Directory Client.
- Updated project file to include necessary package references for the new Issuer Directory Client library.

etc/issuer-directory.yaml.sample

@@ -0,0 +1,22 @@
+IssuerDirectory:
+  telemetry:
+    minimumLogLevel: Information
+  authority:
+    enabled: true
+    issuer: https://authority.example.com/realms/stellaops
+    requireHttpsMetadata: true
+    audiences:
+      - stellaops-platform
+    readScope: issuer-directory:read
+    writeScope: issuer-directory:write
+    adminScope: issuer-directory:admin
+  tenantHeader: X-StellaOps-Tenant
+  seedCsafPublishers: true
+  csafSeedPath: data/csaf-publishers.json
+  Mongo:
+    connectionString: mongodb://localhost:27017
+    database: issuer-directory
+    issuersCollection: issuers
+    issuerKeysCollection: issuer_keys
+    issuerTrustCollection: issuer_trust_overrides
+    auditCollection: issuer_audit