Log the username of CLI users

If the owner isn't running it and the scheduler doesn't have a different
user, then use the operating system getlogin user. Allows for detecting
the user without assuming the user got there through sudo or similar
means

Author: psa

cylc/flow/network/resolvers.py

@@ -21,6 +21,7 @@
 from contextlib import suppress
 from fnmatch import fnmatchcase
 import logging
+import os
 import queue
 from time import time
 from typing import (
@@ -724,10 +725,17 @@ async def _mutation_mapper(
 
         """
         user = meta.get('auth_user', self.schd.owner)
-        if user == self.schd.owner:
+        try:
+            login = os.getlogin()
+        except OSError:
+            # No controlling terminal, we're running as the owner
+            login = self.schd.owner
+        if user == self.schd.owner and login == self.schd.owner:
             log_user = f" from {self.schd.owner}"
-        else:
+        elif login == self.schd.owner:
             log_user = f" from {user}"
+        else:
+            log_user = f" from {login}"
 
         log1 = f'Command "{command}" received{log_user}.'
         log2 = (