fix(provisioning_api): cap group listings and throttle group creation

[pringelmann]

Summary

The two group listing endpoints, /cloud/groups and /cloud/groups/details, returned every group on the instance when no limit was given. The details one is the expensive one, since it counts members per group. Both now default to 500, and requests can page through the rest with offset. Creating a group is rate limited to 50 per ten minutes, matching the other write endpoints here.

Warning

Clients that relied on getting everything back now get the first 500, with nothing in the response to say it was cut off.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI (tests mostly)