[web] also return http_code when trying to create peering when already exists

web/backend/peering_manager.py

@@ -159,7 +159,7 @@ class PeeringManager:
         # deny more than one peering per ASN to one node
         for peering in self.peerings["asn"][asn]:
             if peering["node"] == node:
-                return False
+                return False, 409
 
         peering = {"MNT": mnt, "ASN": asn, "node": node, "wg_key": wg_key, "endpoint": endpoint,
                    "ipv6ll": ipv6ll, "ipv4": ipv4, "ipv6": ipv6, "bgp_mp": bgp_mp, "bgp_enh": bgp_enh}

web/requirements.txt

@@ -1,3 +1,4 @@
 Flask
 waitress
-pyopenssl
+pyopenssl
+requests