Add MongoDB storage library and update acceptance tests with deterministic stubs

- Created StellaOps.Notify.Storage.Mongo project with initial configuration.
- Added expected output files for acceptance tests (at1.txt to at10.txt).
- Added fixture input files for acceptance tests (at1 to at10).
- Created input and signature files for test cases fc1 to fc5.

docs/scripts/sbom-vex/sbom.json

@@ -0,0 +1,8 @@
+{
+  "bomFormat": "CycloneDX",
+  "specVersion": "1.5",
+  "version": 1,
+  "components": [
+    {"type": "container", "name": "example", "version": "1.0.0"}
+  ]
+}