🪣Müsli bucket, slice 0: Rework the finalization process

[fosterfarrell9]

This PR closes a larger architectural gap that was left in #1052 and whose extent became only clear to me when I implemented student performance policies in #1084. The problem is that the old workflow mixed separate things like eligibility checking and allocation/finalization. In practice this meant that students who clearly failed a policy and shouldn't even be considered for free seats were actually allowed to get one, with the "violator dashboard" being the one step that prevented them from getting a seat - and where the teacher had to choose between just giving them a seat or completely hard-deleting their registration (with no trace left for either side what happened). The PR introduces a dedicated screening step before allocation/finalization that classifies outcomes as pass, auto_reject, or blocker. The last one is necessary for situations where data are missing for policy evaluation like missing certificates for student performances. In the new solution, only blockers are being brought to the teachers attention in the finalization process, registrations with auto_reject are automatically rejected, but they are stored, together with their rejection reason. In post-finalization, teachers can clearly distinguish rejected students from merely unassigned ones, inspect the reason, and still manually override by adding them if needed.

In the process of implementing this PR, I got more and more annoyed at the very colorful design of buttons, alerts etc in the allocation and finalization process, so that I finally decided to make the design are little more muted (see the screenshots below). I think this now fits a lot better with the general design in the groups tab.

Since this is slice 0 of the old muesli-bowl and in there the rake tasks providing stuff to play around in the GUI with became a little chaotic, I restructured the whole demo task business. The demo workflow now uses four clearly named tasks:

• demo:flags enables the feature flags needed for the current slice.
• demo:campaigns prepares the reusable campaign examples.
• demo:rosters prepares roster-related demo data (without the need to manually finalize campaigns)
• demo:setup runs the full setup for the current slice.

This gives the demo setup a clearer structure and makes it easier to run exactly the part you need, while keeping the overall workflow consistent as more Muesli features are added in later slices.

Note for the reviewer: In order to get a good feeling of how it works, just run the demo:setup task and finalize all campaigns that this provides (two for Linear Algebra 2 and three for the Campaign Test Seminar).

Implementation notes

• Added policy screening via Registration::ScreeningService and integrated it into allocation/finalization (block on blockers, auto-reject deterministic violators).
• Persisted rejection decisions with additional columns on on Registration::UserRegistration (reason fields + timestamps) and track allocation decisions with the new column allocation_decided_at on Registration::Campaign.

Below are a few screenshots

• Revised color scheme:

• Finalization auto-reject preview:

• flash message after finalization contains info on the number of rejected/unassigned students (if existent)

• new color scheme again:

• new color scheme, also note that the presentation logic for the counts (wording, given numbers) is now more coherent

• campaign dissolved pill now also contains info on rejected students (due to policy vioplations)

• rejected students get their own sidepanel

• rejected students are now also given (as a number) and in a table with rejection reason

[codecov]

Codecov Report

❌ Patch coverage is 49.35401% with 392 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.43%. Comparing base (4c75cda) to head (fc73171).
⚠️ Report is 19 commits behind head on next.

Files with missing lines	Patch %	Lines
lib/demo/campaign_setup_support.rb	7.44%	261 Missing ⚠️
lib/demo/setup_support.rb	22.75%	112 Missing ⚠️
app/helpers/application_helper.rb	42.85%	4 Missing ⚠️
lib/demo/quiet_logging_support.rb	50.00%	4 Missing ⚠️
...lers/registration/user_registrations_controller.rb	87.50%	2 Missing ⚠️
app/models/registration/allocation_dashboard.rb	93.75%	2 Missing ⚠️
app/models/registration/screening_service.rb	96.22%	2 Missing ⚠️
...controllers/registration/allocations_controller.rb	94.11%	1 Missing ⚠️
...d/roster/components/roster_side_panel_component.rb	97.56%	1 Missing ⚠️
app/models/registration/campaign.rb	97.87%	1 Missing ⚠️
... and 2 more

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #1104      +/-   ##
==========================================
+ Coverage   63.97%   64.43%   +0.46%     
==========================================
  Files         415      424       +9     
  Lines       13492    14247     +755     
==========================================
+ Hits         8631     9180     +549     
- Misses       4861     5067     +206     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.