add a comment about why we only split out the wifi config

subiquity/models/network.py

@@ -34,6 +34,11 @@ class NetworkModel(NetworkModel):
 
     def render(self):
         netplan = self.render_config()
+        # We write wifi config -- which almost certainly contains secrets -- to
+        # a separate file with more restrictive permissions. This isn't a
+        # perfect solution because in principle there could be wired 802.1x
+        # stuff that has secrets too but the subiquity UI does not support any
+        # of that yet so this will do for now.
         wifis = netplan['network'].pop('wifis', None)
         r = {
             'write_files': {