auth: clean up remote IP parameter/documentation

Make the remote IP parameter more generic and make it an enum
determining the source instead of a boolean. Also fix the
changelog entry.

Both as requested, I managed to miss those comments previously.

radicale/auth/__init__.py

@@ -64,6 +64,8 @@ INSECURE_IF_NO_LOOPBACK_TYPES: Sequence[str] = (
 
 AUTH_SOCKET_FAMILY: Sequence[str] = ("AF_UNIX", "AF_INET", "AF_INET6")
 
+REMOTE_ADDR_SOURCE: Sequence[str] = ("REMOTE_ADDR", "X-Remote-Addr")
+
 
 def load(configuration: "config.Configuration") -> "BaseAuth":
     """Load the authentication module chosen in configuration."""

radicale/auth/dovecot.py

@@ -33,7 +33,8 @@ class Auth(auth.BaseAuth):
         self.timeout = 5
         self.request_id_gen = itertools.count(1)
 
-        self.use_x_remote_addr = configuration.get("auth", "dovecot_rip_x_remote_addr")
+        remote_ip_source = configuration.get("auth", "remote_ip_source")
+        self.use_x_remote_addr = remote_ip_source == 'X-Remote-Addr'
 
         config_family = configuration.get("auth", "dovecot_connection_type")
         if config_family == "AF_UNIX":