Validate against trailing spaces in Jira Username configuration

Description

Trying to integrate gitlab with jira I was scratching my head on why it didn't run (w/o any sensible information in neither the logs nur the ui after performing a test). Turns out you can enter trailing spaces in the Username field and gitlab doesn't sanitize the input unlike it does seem to perform for the project key.

Proposal

Sanity check Username input the way the Project key already seems to be.

Links / references

Documentation blurb

Overview

What is it? a minor change Why should someone use this feature? If they are dumb like me. What is the underlying (business) problem? Sanity check, UI feedback. How do you use this feature? angrily.

Use cases

People who have to use Jira because they can't have gitlab web-exposed (and can't afford all the additional licenses) and who can't risk having customers accessing code.

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.

• Feature assurance
• Documentation
• Added to features.yml