feat: Implement Scheduler Worker Options and Planner Loop

- Added `SchedulerWorkerOptions` class to encapsulate configuration for the scheduler worker.
- Introduced `PlannerBackgroundService` to manage the planner loop, fetching and processing planning runs.
- Created `PlannerExecutionService` to handle the execution logic for planning runs, including impact targeting and run persistence.
- Developed `PlannerExecutionResult` and `PlannerExecutionStatus` to standardize execution outcomes.
- Implemented validation logic within `SchedulerWorkerOptions` to ensure proper configuration.
- Added documentation for the planner loop and impact targeting features.
- Established health check endpoints and authentication mechanisms for the Signals service.
- Created unit tests for the Signals API to ensure proper functionality and response handling.
- Configured options for authority integration and fallback authentication methods.

src/StellaOps.Concelier.Storage.Mongo/ServiceCollectionExtensions.cs

@@ -12,12 +12,13 @@ using StellaOps.Concelier.Storage.Mongo.Exporting;
 using StellaOps.Concelier.Storage.Mongo.JpFlags;
 using StellaOps.Concelier.Storage.Mongo.MergeEvents;
 using StellaOps.Concelier.Storage.Mongo.Conflicts;
-using StellaOps.Concelier.Storage.Mongo.PsirtFlags;
-using StellaOps.Concelier.Storage.Mongo.Statements;
-using StellaOps.Concelier.Storage.Mongo.Events;
-using StellaOps.Concelier.Core.Events;
+using StellaOps.Concelier.Storage.Mongo.PsirtFlags;
+using StellaOps.Concelier.Storage.Mongo.Statements;
+using StellaOps.Concelier.Storage.Mongo.Events;
+using StellaOps.Concelier.Core.Events;
 using StellaOps.Concelier.Storage.Mongo.Migrations;
 using StellaOps.Concelier.Storage.Mongo.Observations;
+using StellaOps.Concelier.Core.Observations;
 
 namespace StellaOps.Concelier.Storage.Mongo;
 
@@ -73,6 +74,7 @@ public static class ServiceCollectionExtensions
         services.AddSingleton<IAdvisoryStatementStore, AdvisoryStatementStore>();
         services.AddSingleton<IAdvisoryConflictStore, AdvisoryConflictStore>();
         services.AddSingleton<IAdvisoryObservationStore, AdvisoryObservationStore>();
+        services.AddSingleton<IAdvisoryObservationLookup, AdvisoryObservationLookup>();
         services.AddSingleton<IAdvisoryEventRepository, MongoAdvisoryEventRepository>();
         services.AddSingleton<IAdvisoryEventLog, AdvisoryEventLog>();
         services.AddSingleton<IExportStateStore, ExportStateStore>();