fix(spp_programs): stop Enroll Eligible undoing a deliberate pause

[emjay0921]

Why is this change needed?

Pausing a membership is a program officer's explicit decision, meant to be undone only by Resume. Enroll Eligible re-evaluated paused members along with everyone else and wrote them back to enrolled, reversing that decision with no warning (OP#1117). Low frequency, high trust impact: an officer who pauses a beneficiary expects it to stick.

The concept was already half-present in the code — a comment noting that duplicated and exited "should only be changed through their own workflows" — but paused was not in the set.

How was the change implemented?

• The set is now explicit as constants.PROTECTED_MEMBERSHIP_STATES and applied everywhere re-running eligibility decides a membership's state.
• Three paths, not one. The reported symptom is the enrol branch of _enroll_eligible_registrants, but its disenrol sweep had the same gap and would write a paused member the eligibility manager did not return to not_eligible — destroying the pause just as thoroughly. The per-membership enroll_eligible_registrants and verify_eligibility on spp.program.membership were the third: their buttons are hidden unless the record is draft, but the methods are public and reachable over RPC, and the point of the ticket is that a pause should be trustworthy.
• The async branch, taken for programs above MIN_ROW_JOB_QUEUE, dispatches into the same _enroll_eligible_registrants, so both branches are covered. Program-level verify_eligibility passes ["enrolled", "not_eligible"] and never sees paused.
• Nothing outside spp_programs overrides this logic, so SP-MIS and Farmer Registry pick the fix up from the shared code, as the ticket expects.

Deliberately untouched: deduplication still flags a paused member as duplicated. A duplicate is a duplicate regardless of pause, and that is a different action from the one reported here — though it does mean dedup protects exited and not_eligible while leaving paused open.

New unit tests

spp_programs/tests/test_program_enrollment.py — four assertions that a paused membership is still paused after Enroll Eligible (enrol path, disenrol sweep, and the two per-membership methods), plus one that Resume still has something to resume. Written first and confirmed failing against the unfixed code, then passing.

Unit tests executed by the author

Full spp_programs suite on this branch after merging 19.0 in: 684 tests, 0 failed, 0 errors.

How to test manually

1. Open a registrant enrolled in a program, and on the Participation tab click Pause on the membership.
2. Go to the program and click Enroll Eligible.
3. The membership is still Paused — before, it went back to Enrolled.
4. Click Resume on the membership: it returns to Enrolled, which is the only route that should do so.
5. Make a paused member fail the eligibility rules, then run Enroll Eligible again — it stays Paused rather than being swept to not_eligible.

Related links

• OP#1117 — https://projects.acn.fr/work_packages/1117

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.04%. Comparing base (0820667) to head (dec8f8c).

Additional details and impacted files

@@            Coverage Diff             @@
##             19.0     #436      +/-   ##
==========================================
+ Coverage   72.24%   73.04%   +0.80%     
==========================================
  Files         419      480      +61     
  Lines       29813    32228    +2415     
==========================================
+ Hits        21539    23542    +2003     
- Misses       8274     8686     +412     

Flag	Coverage Δ
spp_api_v2_cycles	71.03% <ø> (ø)
spp_api_v2_entitlements	70.23% <ø> (ø)
spp_api_v2_programs	92.22% <ø> (ø)
spp_api_v2_simulation	71.19% <ø> (?)
spp_base_common	91.07% <ø> (ø)
spp_case_entitlements	100.00% <ø> (?)
spp_case_programs	100.00% <ø> (?)
spp_cr_type_assign_program	92.07% <ø> (ø)
spp_dci_compliance	93.01% <ø> (?)
spp_dci_demo	94.28% <ø> (ø)
spp_dci_server_social	89.57% <ø> (?)
spp_farmer_registry_demo	61.06% <ø> (ø)
spp_gis_report_programs	100.00% <ø> (?)
spp_grm_demo	80.13% <ø> (?)
spp_grm_programs	92.13% <ø> (?)
spp_hazard_programs	98.55% <ø> (?)
spp_programs	65.53% <100.00%> (+0.25%)	⬆️
spp_registry	87.22% <ø> (+0.07%)	⬆️
spp_security	69.56% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
spp_programs/models/constants.py	100.00% <100.00%> (ø)
spp_programs/models/managers/program_manager.py	86.47% <100.00%> (+0.08%)	⬆️
spp_programs/models/program_membership.py	67.33% <100.00%> (+8.54%)	⬆️

... and 63 files with indirect coverage changes

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