Implement ledger metrics for observability and add tests for Ruby packages endpoints

- Added `LedgerMetrics` class to record write latency and total events for ledger operations.
- Created comprehensive tests for Ruby packages endpoints, covering scenarios for missing inventory, successful retrieval, and identifier handling.
- Introduced `TestSurfaceSecretsScope` for managing environment variables during tests.
- Developed `ProvenanceMongoExtensions` for attaching DSSE provenance and trust information to event documents.
- Implemented `EventProvenanceWriter` and `EventWriter` classes for managing event provenance in MongoDB.
- Established MongoDB indexes for efficient querying of events based on provenance and trust.
- Added models and JSON parsing logic for DSSE provenance and trust information.

src/StellaOps.Events.Mongo/StellaOps.Events.Mongo.csproj

@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="MongoDB.Driver" Version="3.5.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="../__Libraries/StellaOps.Provenance.Mongo/StellaOps.Provenance.Mongo.csproj" />
+  </ItemGroup>
+
+</Project>