Add APRS-IS support

data/spot.py

@@ -40,6 +40,9 @@ class Spot:
     dx_cq_zone: int = None
     # ITU zone of the DX operator
     dx_itu_zone: int = None
+    # If this is an APRS spot, what SSID was the DX operator using?
+    # This is a string not an int for now, as I often see non-numeric ones somehow
+    dx_aprs_ssid: str = None
     # Reported mode, such as SSB, PHONE, CW, FT8...
     mode: str = None
     # Inferred mode "family". One of "CW", "PHONE" or "DIGI".