Add comprehensive security tests for OWASP A03 (Injection) and A10 (SSRF)

- Implemented InjectionTests.cs to cover various injection vulnerabilities including SQL, NoSQL, Command, LDAP, and XPath injections.
- Created SsrfTests.cs to test for Server-Side Request Forgery (SSRF) vulnerabilities, including internal URL access, cloud metadata access, and URL allowlist bypass attempts.
- Introduced MaliciousPayloads.cs to store a collection of malicious payloads for testing various security vulnerabilities.
- Added SecurityAssertions.cs for common security-specific assertion helpers.
- Established SecurityTestBase.cs as a base class for security tests, providing common infrastructure and mocking utilities.
- Configured the test project StellaOps.Security.Tests.csproj with necessary dependencies for testing.

src/Policy/StellaOps.Policy.Engine/stryker-config.json

@@ -0,0 +1,43 @@
+{
+  "$schema": "https://raw.githubusercontent.com/stryker-mutator/stryker-net/master/src/Stryker.Core/Stryker.Core/config-schema.json",
+  "stryker-config": {
+    "project-info": {
+      "name": "StellaOps.Policy",
+      "module": "Policy.Engine",
+      "version": "0.0.1"
+    },
+    "solution": "../../../StellaOps.Router.slnx",
+    "project": "StellaOps.Policy.Engine.csproj",
+    "test-projects": [
+      "../__Tests/StellaOps.Policy.Engine.Tests/StellaOps.Policy.Engine.Tests.csproj"
+    ],
+    "reporters": [
+      "html",
+      "json",
+      "progress"
+    ],
+    "thresholds": {
+      "high": 85,
+      "low": 70,
+      "break": 60
+    },
+    "mutation-level": "Standard",
+    "mutators": {
+      "included": [
+        "Arithmetic",
+        "Boolean",
+        "Comparison",
+        "Conditional",
+        "Equality",
+        "Logical",
+        "NullCoalescing"
+      ]
+    },
+    "coverage-analysis": "perTest",
+    "excluded-files": [
+      "**/Generated/**/*",
+      "**/Rego/**/*"
+    ],
+    "output-path": "../../../.stryker/output/policy-engine"
+  }
+}