[#69702] Primerize API settings form

[myabc]

⚠️ This PR is based on #21601. Please view/merge that PR first.

Ticket

https://community.openproject.org/wp/69702

What are you trying to accomplish?

Primerize the API Settings form. Uses the fieldset_group input group introduced in #21601.

Screenshots

What approach did you choose and why?

A best effort.

The "warning text" styling still needs to be discuss.

Merge checklist

• [X] Added/updated tests
• [X] Added/updated documentation in Lookbook (patterns, previews, etc)
• [X] Tested major browsers (Chrome, Firefox, Edge, ...)

[myabc]

The changes itself look good. I am personally not a big fan of the name InlineMessage

It was previously named WarningText. However i've changed it as it should now behave exactly like a Primer InlineMessage.

[HDinger]

The changes itself look good. I am personally not a big fan of the name InlineMessage

It was previously named WarningText. However i've changed it as it should now behave exactly like a Primer InlineMessage.

Okay, so it belongs to the PVC repo after all 👍