Idea Summary
Constraints are a good way to maintain your database integrity. If you want to show a user-friendly message when a constraint is violated, you have to write a validation to check the constraint before it's violated, just to show your custom message. This leads to a large amount of validations being written and maintained just to get a clean message (your database is already protected by the constraint, it doesn't need the validation whatsoever). Development would be noticeably faster if you didn't need to write a validation for every constraint in every page it can gets violated just to get a friendly error message.
Inside SQL Workshop, on UI Defaults, let developers configure a friendly error message for each constraint in the database. Having this would mean the need for custom validations in applications would drop significantly (in my case over 60%), enhancing productivity by a fair margin. The application would also be cleaner, easier to maintain and more consistent.