Try harder to derive the username from email addresses

Some providers set username or nickname to an email address.
For this reason, first collect the best possible user name we can find,
and only then fix it to match our requirements.

Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>

src/api/app/controllers/webui/user_controller.rb

@@ -300,10 +300,19 @@ class Webui::UserController < Webui::WebuiController
       return
     end
 
+    # Try to derive a username from the information available,
+    # falling back to full name if nothing else works
     @derived_username = auth_hash['info']['username'] ||
                         auth_hash['info']['nickname'] ||
-                        auth_hash['info']['email'].rpartition("@")[0] ||
-                        auth_hash['info']['name'].gsub(' ', '_')
+                        auth_hash['info']['email'] ||
+                        auth_hash['info']['name']
+
+    # Some providers set username or nickname to an email address
+    # Derive the username from the local part of the email address,
+    # if possible. The full name with spaces replaced by underscores
+    # is the last resort fallback.
+    @derived_username = @derived_username.rpartition("@")[0] if @derived_username.include? "@"
+    @derived_username = @derived_username.gsub(' ', '_')
   end
 
   def do_sso_confirm