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.Policy/PolicyDigest.cs

@@ -46,16 +46,50 @@ public static class PolicyDigest
         }
 
         writer.WritePropertyName("rules");
-        writer.WriteStartArray();
-        foreach (var rule in document.Rules)
-        {
-            WriteRule(writer, rule);
-        }
-        writer.WriteEndArray();
-
-        writer.WriteEndObject();
-        writer.Flush();
-    }
+        writer.WriteStartArray();
+        foreach (var rule in document.Rules)
+        {
+            WriteRule(writer, rule);
+        }
+        writer.WriteEndArray();
+
+        if (!document.Exceptions.Effects.IsDefaultOrEmpty || !document.Exceptions.RoutingTemplates.IsDefaultOrEmpty)
+        {
+            writer.WritePropertyName("exceptions");
+            writer.WriteStartObject();
+
+            if (!document.Exceptions.Effects.IsDefaultOrEmpty)
+            {
+                writer.WritePropertyName("effects");
+                writer.WriteStartArray();
+                foreach (var effect in document.Exceptions.Effects
+                             .OrderBy(static e => e.Id, StringComparer.Ordinal))
+                {
+                    WriteExceptionEffect(writer, effect);
+                }
+
+                writer.WriteEndArray();
+            }
+
+            if (!document.Exceptions.RoutingTemplates.IsDefaultOrEmpty)
+            {
+                writer.WritePropertyName("routingTemplates");
+                writer.WriteStartArray();
+                foreach (var template in document.Exceptions.RoutingTemplates
+                             .OrderBy(static t => t.Id, StringComparer.Ordinal))
+                {
+                    WriteExceptionRoutingTemplate(writer, template);
+                }
+
+                writer.WriteEndArray();
+            }
+
+            writer.WriteEndObject();
+        }
+
+        writer.WriteEndObject();
+        writer.Flush();
+    }
 
     private static void WriteRule(Utf8JsonWriter writer, PolicyRule rule)
     {
@@ -193,19 +227,78 @@ public static class PolicyDigest
         writer.WriteEndArray();
     }
 
-    private static void WriteStringArray(Utf8JsonWriter writer, string propertyName, ImmutableArray<string> values)
-    {
-        if (values.IsDefaultOrEmpty)
-        {
-            return;
-        }
-
-        writer.WritePropertyName(propertyName);
-        writer.WriteStartArray();
-        foreach (var value in values)
-        {
-            writer.WriteStringValue(value);
-        }
-        writer.WriteEndArray();
-    }
-}
+    private static void WriteStringArray(Utf8JsonWriter writer, string propertyName, ImmutableArray<string> values)
+    {
+        if (values.IsDefaultOrEmpty)
+        {
+            return;
+        }
+
+        writer.WritePropertyName(propertyName);
+        writer.WriteStartArray();
+        foreach (var value in values)
+        {
+            writer.WriteStringValue(value);
+        }
+        writer.WriteEndArray();
+    }
+
+    private static void WriteExceptionEffect(Utf8JsonWriter writer, PolicyExceptionEffect effect)
+    {
+        writer.WriteStartObject();
+        writer.WriteString("id", effect.Id);
+
+        if (!string.IsNullOrWhiteSpace(effect.Name))
+        {
+            writer.WriteString("name", effect.Name);
+        }
+
+        writer.WriteString("effect", effect.Effect.ToString().ToLowerInvariant());
+
+        if (effect.DowngradeSeverity is { } downgradeSeverity)
+        {
+            writer.WriteString("downgradeSeverity", downgradeSeverity.ToString());
+        }
+
+        if (!string.IsNullOrWhiteSpace(effect.RequiredControlId))
+        {
+            writer.WriteString("requiredControlId", effect.RequiredControlId);
+        }
+
+        if (!string.IsNullOrWhiteSpace(effect.RoutingTemplate))
+        {
+            writer.WriteString("routingTemplate", effect.RoutingTemplate);
+        }
+
+        if (effect.MaxDurationDays is int maxDurationDays)
+        {
+            writer.WriteNumber("maxDurationDays", maxDurationDays);
+        }
+
+        if (!string.IsNullOrWhiteSpace(effect.Description))
+        {
+            writer.WriteString("description", effect.Description);
+        }
+
+        writer.WriteEndObject();
+    }
+
+    private static void WriteExceptionRoutingTemplate(Utf8JsonWriter writer, PolicyExceptionRoutingTemplate template)
+    {
+        writer.WriteStartObject();
+        writer.WriteString("id", template.Id);
+        writer.WriteString("authorityRouteId", template.AuthorityRouteId);
+
+        if (template.RequireMfa)
+        {
+            writer.WriteBoolean("requireMfa", true);
+        }
+
+        if (!string.IsNullOrWhiteSpace(template.Description))
+        {
+            writer.WriteString("description", template.Description);
+        }
+
+        writer.WriteEndObject();
+    }
+}