Properly handle user profiles without names

If user is mentioned only as co-author in commit and has no
other contribution, nor registered at Launchpad then a profile
is created with empty name. Since the name is required across
the code, use user_id instead of it.

Change-Id: I87bb9cf186d05a6f1299f3150306dcbc01b02fdc

stackalytics/dashboard/web.py

@@ -453,7 +453,7 @@ def get_users_json(record_ids, **kwargs):
     result = []
     for user_id in user_ids:
         user = vault.get_user_from_runtime_storage(user_id)
-        r = {'id': user_id, 'text': user['user_name']}
+        r = {'id': user_id, 'text': user.get('user_name') or user['user_id']}
 
         add_flag = not core_in
         if core_in and user.get('core'):

stackalytics/processor/user_processor.py

@@ -208,6 +208,10 @@ def merge_user_profiles(domains_index, user_profiles):
     merged_user['user_id'] = (merged_user.get('launchpad_id') or
                               merged_user.get('user_id'))
 
+    # always preserve `user_name` since its required field
+    if 'user_name' not in merged_user:
+        merged_user['user_name'] = merged_user['user_id']
+
     # merge emails
     emails = set([])
     core_in = set([])