Allow defaulting to remove source branch when merge request is accepted

Problem to solve

We have a policy of deleting the source branch when merge requests are accepted. When creating a merge request there's a checkbox to perform this task automatically but that box is unchecked by default, wasting precious milliseconds from our merge request creation by requiring one more click.

Proposal

An option in the settings to have that box checked by default would mean a minimal but welcome QOL improvement in our daily lives.

What does success look like, and how can we measure that?

Quicker merge request creation and lower chance for setting incorrect parameters when creating merge requests early in the morning.