feat: implement MailGun webhook service for logging email events

Implemented a production-ready TypeScript/Express.js service to receive
and log MailGun webhook events (delivered, failed, opened, clicked, etc.).

Key features:
- Webhook endpoint (POST /webhook) with comprehensive event logging
- Full TypeScript type definitions for all MailGun event types
- Prometheus metrics integration for monitoring
- Health check endpoint (GET /ping)
- Comprehensive Jest test suite with 87.76% coverage
- Docker containerization with build scripts

Removed template/example code:
- All SQL/MSSQL dependencies and related code
- Example auth router and middleware
- PRTG metrics support (simplified to Prometheus only)
- Unused middleware (CORS, IP whitelist, request parsing/validation)
- Template documentation (kept only MailGun webhook API spec)

The service is clean, minimal, and focused solely on receiving and
logging MailGun webhook events to the console.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

mailgun-webhook/package.json

@@ -0,0 +1,51 @@
+{
+  "name": "mailgun-webhook-service",
+  "version": "1.0.0",
+  "description": "MailGun webhook receiver service for logging email event notifications",
+  "main": "entry.ts",
+  "scripts": {
+    "start": "nodemon ./src/entry.ts",
+    "build": "ttsc --project ./",
+    "test": "jest --watch",
+    "test:ci": "jest --ci --coverage --watchAll=false",
+    "test:coverage": "jest --coverage",
+    "lint": "tsc --noEmit",
+    "type-check": "tsc --noEmit",
+    "run-server": "DEBUG=* node --enable-source-maps ./build/entry.js"
+  },
+  "author": "Nikola",
+  "license": "ISC",
+  "dependencies": {
+    "debug": "^2.6.9",
+    "express": "^4.18.2",
+    "http-errors": "^1.7.2",
+    "prom-client": "^14.0.1",
+    "stoppable": "^1.1.0"
+  },
+  "devDependencies": {
+    "@babel/preset-typescript": "^7.18.6",
+    "@types/debug": "^4.1.7",
+    "@types/express": "^4.17.13",
+    "@types/http-errors": "^1.8.1",
+    "@types/jest": "^29.2.5",
+    "@types/node": "^16.10.2",
+    "@types/stoppable": "^1.1.1",
+    "@types/supertest": "^2.0.11",
+    "@zerollup/ts-transform-paths": "^1.7.18",
+    "esbuild": "^0.16.14",
+    "esbuild-jest": "^0.5.0",
+    "jest": "^29.3.1",
+    "nodemon": "^2.0.13",
+    "supertest": "^6.3.3",
+    "ts-node": "^10.9.1",
+    "tsconfig-paths": "^4.1.2",
+    "ttypescript": "^1.5.15",
+    "typescript": "^4.9.4",
+    "typescript-transform-paths": "^3.4.4"
+  },
+  "babel": {
+    "presets": [
+      "@babel/preset-typescript"
+    ]
+  }
+}