Make AutoTimestampEventListener temporary disabling thread-safe (8.0.x)

[codeconsole]

Fixes #14510 on 8.0.x. Identical to the 7.1.x port #15953 (this class is byte-identical on 7.1.x through 8.0.x — the cherry-pick applied with zero conflicts); see also the original 7.0.x fix #15952.

The bug

withoutTimestamps, withoutDateCreated and withoutLastUpdated disabled timestamping by mutating the listener-wide entity maps (capturing each entry and setting it to Optional.empty(), then restoring). That state is JVM-global, so overlapping windows on concurrent threads corrupt each other:

1. Thread A enters: captures ON, sets OFF
2. Thread B enters: captures OFF, sets OFF
3. Thread A exits: restores ON
4. Thread B's save now runs with timestamping — its historical dateCreated/lastUpdated values are silently clobbered

Reproduction: https://github.com/codeconsole/grails-autotimestamp-bug

A second facet: there was no try/finally, so an exception inside the closure left timestamping permanently disabled for the whole JVM.

The fix

The shared metadata maps are no longer mutated. Suppression is tracked per thread: the property-name getters consult a ThreadLocal holding an all-entities nesting depth plus the set of entity names disabled by per-class scopes. Each scope only re-enables the names it added, so nested and overlapping scopes restore correctly; try/finally guarantees restoration when the closure throws; the ThreadLocal is removed when empty so nothing is retained on pooled threads.

Public API, protected fields and single-thread semantics are unchanged (binary and source compatible). The CreatedBy/UpdatedBy auditing maps are untouched — no withoutXxx API covers them.

Merge coordination

Once this and #15953 are both merged, the routine 7.1.x → 7.2.x → 8.0.x cascade merges see identical content on both sides and resolve cleanly. The only conflicted hop is 7.0.x → 7.1.x after #15952, which resolves as keep-7.1.x's-listener.

Behavioral note

Disabling is now scoped to the calling thread. Threads spawned inside the closure are no longer affected — under the old global behavior they were (by accident). Code relying on that must call withoutTimestamps on each thread. The auto-timestamping guide now documents the thread scoping. Worth a mention in the release notes.

Tests

The spec exercises the listener through the public beforeInsert/beforeUpdate API, with tests that reproduce the bug (verified red on the unfixed listener on 7.0.x and 7.1.x, whose suppression code is identical to 8.0.x's):

• cross-thread isolation (the main GRAILS 6+ BUG: autoTimestampEventListener.without* Results in Unexpected Behavior Across All Threads #14510 repro)
• overlapping windows on different threads restoring independently (the interleaving above)
• nested and overlapping same-class scopes restoring the enclosing scope
• restoration when the closure throws, including a partial failure while registering a class list
• an 8-thread contention stress test

All 248 tests in grails-datamapping-core pass on the 8.0.x toolchain (JDK 25/Groovy 5), as do the timestamp specs in grails-datamapping-core-test, grails-data-hibernate5-core and grails-test-suite-uber; Checkstyle and CodeNarc are clean.

[codecov]

Codecov Report

❌ Patch coverage is 97.36842% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 49.5213%. Comparing base (fa25f0a) to head (c3289a8).

Files with missing lines	Patch %	Lines
...astore/gorm/events/AutoTimestampEventListener.java	97.3684%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##                8.0.x     #15954        +/-   ##
==================================================
+ Coverage     49.5127%   49.5213%   +0.0086%     
- Complexity      16895      16901         +6     
==================================================
  Files            1998       1998                
  Lines           93679      93695        +16     
  Branches        16402      16403         +1     
==================================================
+ Hits            46383      46399        +16     
+ Misses          40139      40138         -1     
- Partials         7157       7158         +1     

Files with missing lines	Coverage Δ
...astore/gorm/events/AutoTimestampEventListener.java	67.8392% <97.3684%> (+2.2654%)	⬆️

... and 1 file with indirect coverage changes

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[testlens-app]

✅ All tests passed ✅

🏷️ Commit: c3289a8
▶️ Tests: 28018 executed
⚪️ Checks: 59/59 completed

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