Draft: The Store Model Purge, a Tragedy in 3 Acts. Act 2.

⚠ This MR has been folded into !1811 (merged) ⚠

What does this MR do?

PLEASE READ: this is a "review only" merge request to split big changes into smaller chunks. it's continued in !1811 (merged) where some of the missing functionality is implemented.

• reimplement moving store team members to or from standby team in REST
• reimplement xhr_warteRequest in REST, remove that StoreModel part
• refactor StoreModel::teamRequest with StoreTransactions and in REST
• UI skeleton: new simple dialog to add users to store team, and buttons to promote/demote store managers

This merge request is not meant to be merged on its own! ⚠

Best review commit by commit.

How confident are you it won't break things if deployed?

• ⚠ it will break, so it must not be merged on its own ⚠

Links to related issues

• the changes in here are part of !1811 (merged)
• based on a mix of pickup-gateway and my earlier drafts from !1781 (closed) to incorporate a thorough removal process
• more groundwork for #1029 (closed) and partially for #1012 (closed)
• !1800 (merged)
• !1809 (merged)
• !1810 (closed) <- you are here
• !1811 (merged)
• !1814 (merged)

How to test

• apply for store team and send request to standby team (waiting list / jumpers)
• move existing team members to and from standby team (just like before, no UI change)
• get familiar with the store-team management mode. if enabled, you should see an input field to add new team members, and buttons to promote / demote store managers. they will not work yet!

Screenshots

Checklist

• added a test, or explain why one is not needed/possible...
• no unrelated changes
• asked someone for a code review
• set a "for:" label to indicate who will be affected by this change
• use "state:" labels to track this MR's state until it was beta tested
• added an entry to CHANGELOG.md
• release notes => !1811 (merged)
• beta testing => !1811 (merged)