feat(soft-delete): warn at startup when the purge beat entry is missing

[mikebridge]

SUMMARY

Operators who redefine CeleryConfig in superset_config.py — instead of subclassing or merging the default — silently lose beat-schedule entries. For the soft-delete purge task (deletion_retention.purge_soft_deleted) this failure mode is invisible until it matters: archived objects accumulate forever instead of purging after the retention window.

This generalizes the existing startup check for the version-history retention entry (_warn_if_retention_beat_missing) to also cover the purge task:

• The version-history entry is checked unconditionally, as before (shadow rows written by prior deploys keep ageing even when capture is off).
• The purge entry is checked only when the SOFT_DELETE feature flag resolves on at the config level (DEFAULT_FEATURE_FLAGS merged with FEATURE_FLAGS, matching FeatureFlagManager.init_app order). The purge task itself no-ops while the flag is off, so a missing entry is only actionable once soft delete is live. Flags supplied dynamically via GET_FEATURE_FLAGS_FUNC are deliberately not consulted — this is a configuration-only startup diagnostic.

All four documented CELERY_CONFIG shapes (None, class/module, dict, dotted string) behave as before, and matching is by each entry's task value, not the schedule key, so a correctly-scheduled task under a renamed key does not warn.

This is groundwork for eventually enabling SOFT_DELETE by default: the warning must exist before any release ships with soft delete on, so deployments with hand-rolled Celery configs learn about the missing purge entry from the deploy log rather than from unbounded growth.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A — log-only change. New warning text:

soft-delete: CELERY_CONFIG.beat_schedule is missing the 'deletion_retention.purge_soft_deleted' entry — archived objects will never be purged and will accumulate indefinitely. Either inherit from the default CeleryConfig or add the entry to your override.

TESTING INSTRUCTIONS

1. pytest tests/unit_tests/initialization_test.py -k RetentionBeatWarning — 12 tests: 7 pre-existing plus 5 new covering the purge entry (warn when flag on + entry missing, silent when flag off, FEATURE_FLAGS override beats the default, silent when both entries present, renamed-key parity).
2. Manually: set FEATURE_FLAGS = {"SOFT_DELETE": True} and a CELERY_CONFIG class without the purge entry in superset_config.py; start the app; the warning above appears once at startup. Restore the default CeleryConfig; no warning.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags: SOFT_DELETE (the new warning only fires when it resolves on)
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
• Introduces new feature or API
• Removes existing feature or API

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.44%. Comparing base (7d2b184) to head (a0c35eb).

Files with missing lines	Patch %	Lines
superset/initialization/__init__.py	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #42641      +/-   ##
==========================================
- Coverage   65.44%   65.44%   -0.01%     
==========================================
  Files        2810     2810              
  Lines      159362   159366       +4     
  Branches    36372    36373       +1     
==========================================
- Hits       104301   104300       -1     
- Misses      53019    53022       +3     
- Partials     2042     2044       +2     

Flag	Coverage Δ
hive	38.09% <50.00%> (+<0.01%)	⬆️
mysql	57.82% <50.00%> (-0.01%)	⬇️
postgres	57.86% <50.00%> (-0.01%)	⬇️
presto	39.98% <50.00%> (+<0.01%)	⬆️
python	59.25% <50.00%> (-0.01%)	⬇️
sqlite	57.49% <50.00%> (-0.01%)	⬇️
unit	100.00% <ø> (ø)

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