support custom location for database persistent statefile (defaults to "capport.state" in cwd)

src/capport/comm/hub.py

@@ -299,11 +299,11 @@ class Hub:
         self._hostname = socket.getfqdn()
         self._app = app
         self._is_controller = is_controller
-        state_filename: typing.Optional[str]
+        state_filename: str
         if is_controller:
-            state_filename = 'capport.state'
+            state_filename = config.database_file
         else:
-            state_filename = None
+            state_filename = ''
         self.database = capport.database.Database(state_filename=state_filename)
         self._anon_context = ssl.SSLContext()
         # python ssl doesn't support setting tls1.3 ciphers yet, so make sure we stay on 1.2 for now to enable anon