Switch to using the From header for device ID

It appears the From header is actually more meaningingful for calls
coming from Asterisk, as the Contact header does not distinguish between
which device initiated a call like the From header does.

voip_utils/sip.py

@@ -86,12 +86,12 @@ def datagram_received(self, data: bytes, addr):
 
             caller_uri = None
             caller_name = None
-            # The Contact header should give us the URI used for sending SIP messages to the device
-            if headers.get("contact") is not None:
-                caller_uri, caller_name = self._parse_uri_header(headers.get("contact"))
-            # We can try using the From header as a fallback
-            elif headers.get("from") is not None:
+            # The From header should give us the URI used for sending SIP messages to the device
+            if headers.get("from") is not None:
                 caller_uri, caller_name = self._parse_uri_header(headers.get("from"))
+            # We can try using the Contact header as a fallback
+            elif headers.get("contact") is not None:
+                caller_uri, caller_name = self._parse_uri_header(headers.get("contact"))
             # If all else fails try to generate a URI based on the IP and port from the address the message came from
             else:
                 caller_uri = "sip:" + caller_ip + ":" + caller_sip_port