Redmine

When editing members for a project:

If you select a user and click "Add" twice before the server request is completed, it will add a duplicate member record. It then shows up as two items in the projects dropdown menu, and probably other side-effects.

Possible solutions:

1. Add a unique key on `members (user_id, project_id)`
2. Prevent accidental re-submit on the front end, by disabling the button until ajax completes.