naming: prefer displayName over cn/sn

Now we have on-boarded users, move away from being compatible with the authenticator to using displayName in preference to cn/sn.

In local testing here, this change affects just shy of 20% of users in Google so this should be paired with a manual synchronisation run.

INFO:gsuitesync:Loading configuration    
INFO:gsuitesync.sync:Performing synchronisation in READ ONLY mode.    
INFO:gsuitesync.gapiauth:Loading Google account credentials from "./credentials.json"    
INFO:gsuitesync.sync:Reading eligible user entries from LDAP    
INFO:gsuitesync.sync:Total LDAP entries: 59932    
INFO:gsuitesync.sync:Reading managed user entries from LDAP    
INFO:gsuitesync.sync:Total managed user entries: 59932    
INFO:gsuitesync.sync:Getting information on Google domain users    
INFO:gsuitesync.sync:Ignoring users whose organization unit path matches '^/Service Accounts$'    
INFO:gsuitesync.sync:Total Google users: 61558    
INFO:gsuitesync.sync:Suspended Google users: 1626    
INFO:gsuitesync.sync:Calculating updates...    
INFO:gsuitesync.sync:Number of existing users to update: 12034    
INFO:gsuitesync.sync:Number of users to add: 0    
INFO:gsuitesync.sync:Number of users to reactivate: 0    
INFO:gsuitesync.sync:Number of users to suspend: 0    
INFO:gsuitesync.sync:Configuration will modify 19.55% of users    

Closes #5 (closed)

gsuitesync/naming.py

@@ -38,26 +38,6 @@ def get_names(*, uid, display_name=None, cn=None, sn=None):
     Names(given_name='Stephen',
           family_name='Quill-RomanXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX')
 
-    For compatibility with the existing authenticator, if we have common name and surname and the
-    common name ends with the surname, this is used to form the given names assuming there is some
-    string left. (Once we're happy with the sync, we should remove this.)
-
-    >>> get_names(uid='spqr1', sn='Quill Roman', cn='Prof. S.P. Quill Roman')
-    Names(given_name='Prof. S.P.', family_name='Quill Roman')
-
-    For similar compatibility reasons, if we have a cn, split it at the final space character
-    irrespective of display name.
-
-    >>> get_names(uid='spqr1', cn='Prof. S.P. Quill Roman', display_name='Foo Bar')
-    Names(given_name='Prof. S.P. Quill', family_name='Roman')
-    >>> get_names(
-    ...     uid='spqr1', sn='spqr1', display_name='Stephen P. Q. Roman',
-    ...     cn='Prof. S.P.Q. Roman')
-    Names(given_name='Prof. S.P.Q.', family_name='Roman')
-
-    (In the future we will probably remove the compatibility layer but not until we're happy with
-    the rest of the sync.)
-
     If we have display name and surname and the display name ends with the surname, this is used to
     form the given names assuming there is some string left.
 
@@ -73,6 +53,19 @@ def get_names(*, uid, display_name=None, cn=None, sn=None):
     >>> get_names(uid='spqr1', display_name='Stephen Quill Roman')
     Names(given_name='Stephen Quill', family_name='Roman')
 
+    If we have common name and surname and the common name ends with the surname, this is used to
+    form the given names assuming there is some string left.
+
+    >>> get_names(uid='spqr1', sn='Quill Roman', cn='Prof. S.P. Quill Roman')
+    Names(given_name='Prof. S.P.', family_name='Quill Roman')
+
+    If we *only* have a cn, split it at the final space character.
+
+    >>> get_names(uid='spqr1', cn='Prof. S.P. Quill Roman')
+    Names(given_name='Prof. S.P. Quill', family_name='Roman')
+    >>> get_names(uid='spqr1', sn='spqr1', cn='Prof. S.P.Q. Roman')
+    Names(given_name='Prof. S.P.Q.', family_name='Roman')
+
     Support Wookey.
 
     >>> get_names(uid='spqr1', display_name='Wookey')
@@ -102,30 +95,30 @@ def get_names(*, uid, display_name=None, cn=None, sn=None):
     def _make_ret(*, family_name, given_name):
         return Names(family_name=_clean(family_name)[:60], given_name=_clean(given_name)[:40])
 
-    # If we have a sn and cn and the cn ends with sn, split out the sn.
-    if cn is not None and sn is not None and cn.endswith(sn):
-        given_name = cn[:-len(sn)].strip()
+    # If we have a sn and display name and the display name ends with sn, split out the sn.
+    if display_name is not None and sn is not None and display_name.endswith(sn):
+        given_name = display_name[:-len(sn)].strip()
         if given_name != '':
             return _make_ret(family_name=sn, given_name=given_name)
 
-    # If we have cn, split at space and see if we have two parts.
-    if cn is not None:
-        components = cn.split()
+    # If we have the display name, split at space and see if we have two parts.
+    if display_name is not None:
+        components = display_name.split()
         if len(components) > 0:
             family_name = components[-1]
             given_name = ' '.join(components[:-1])
             if given_name != '' and family_name != '':
                 return _make_ret(family_name=family_name, given_name=given_name)
 
-    # If we have a sn and display name and the display name ends with sn, split out the sn.
-    if display_name is not None and sn is not None and display_name.endswith(sn):
-        given_name = display_name[:-len(sn)].strip()
+    # If we have a sn and cn and the cn ends with sn, split out the sn.
+    if cn is not None and sn is not None and cn.endswith(sn):
+        given_name = cn[:-len(sn)].strip()
         if given_name != '':
             return _make_ret(family_name=sn, given_name=given_name)
 
-    # If we have the display name, split at space and see if we have two parts.
-    if display_name is not None:
-        components = display_name.split()
+    # If we have cn, split at space and see if we have two parts.
+    if cn is not None:
+        components = cn.split()
         if len(components) > 0:
             family_name = components[-1]
             given_name = ' '.join(components[:-1])