Add integration tests for migration categories and execution

- Implemented MigrationCategoryTests to validate migration categorization for startup, release, seed, and data migrations.
- Added tests for edge cases, including null, empty, and whitespace migration names.
- Created StartupMigrationHostTests to verify the behavior of the migration host with real PostgreSQL instances using Testcontainers.
- Included tests for migration execution, schema creation, and handling of pending release migrations.
- Added SQL migration files for testing: creating a test table, adding a column, a release migration, and seeding data.

NuGet.config

@@ -3,9 +3,17 @@
   <packageSources>
     <clear />
     <add key="local" value="local-nugets" />
-    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+    <add key="ablera-mirror" value="https://mirrors.ablera.dev/nuget/nuget-mirror/v3/index.json" />
   </packageSources>
   <config>
     <add key="globalPackagesFolder" value="local-nugets/packages" />
   </config>
+  <packageSourceMapping>
+    <packageSource key="local">
+      <package pattern="*" />
+    </packageSource>
+    <packageSource key="ablera-mirror">
+      <package pattern="*" />
+    </packageSource>
+  </packageSourceMapping>
 </configuration>