added definitions of flask app

code/app.py

@@ -0,0 +1,38 @@
+from flask import Flask, request, jsonify
+import os
+from dotenv import load_dotenv
+from ipaddress import ip_address, ip_network
+import logging
+
+load_dotenv()
+app = Flask(__name__)
+
+@app.before_request
+def check_authorized():
+    """
+    Ensure request from allowed ip.
+    """
+    # prepare variables
+    assert 'ALLOWED_IP_RANGE' in os.environ
+    allowed_ip_range = ip_network(os.getenv['ALLOWED_IP_RANGE'])
+    requesting_ip = ip_address(request.remote_addr)
+    # check that requesting ip is allowed
+    if requesting_ip not in allowed_ip_range:
+        logging.info(f'received request from unauthorised ip: {request.remote_addr}')
+        return jsonify(status='forbidden'), 403
+    logging.info(f'received request from {request.remote_addr}')
+
+@app.before_request
+def check_media_type():
+    """
+    Ensure correct Content-Type of request
+    """
+    if not request.headers.get('Content-Type').lower().startswith('application/json'):
+        logging.error(f'received request with wrong content type')
+        return jsonify(status='unsupported media type'), 415
+    
+@app.route('/test', methods=['POST'])
+def test():
+    logging.debug(request.get_json(force=True))
+    return jsonify(status='success', sender=request.remote_addr)
+