Add specs and clean up transactions.transform/transform in grails-datamapping-core

[borinquenkid]

Summary

• Closes direct unit-spec coverage gaps in org.grails.datastore.gorm.transactions.transform and org.grails.datastore.gorm.transform left after Add test coverage and fix compiler crashes in GORM AST transforms #16148: RollbackTransform, AbstractDatastoreMethodDecoratingTransformation, AbstractMethodDecoratingTransformation, AstMethodDispatchUtils, and AstPropertyResolveUtils.
• Writing the AstPropertyResolveUtils spec surfaced a real correctness bug: its property cache was keyed by class name (a String), so two distinct ClassNode instances sharing a name (e.g. from separate compilations of dynamically-generated/test classes) silently corrupted each other's cached property data under concurrent use. Fixed by keying the cache on ClassNode identity via a synchronized IdentityHashMap.
• Extracted the duplicated applied-marker idempotency check/mark pattern (repeated across AbstractGormASTTransformation, AbstractMethodDecoratingTransformation, and AbstractDatastoreMethodDecoratingTransformation) into shared isAlreadyApplied/markApplied helpers.
• Small cleanups flagged by static analysis: equals() calls replaced with ==, an unused method parameter removed, Java 21 instanceof pattern variables replacing raw-type casts, String#isEmpty() over length()==0, Class#getDeclaredConstructor().newInstance() over the deprecated Class#newInstance(), and two stray doc/comment fixes.

Test plan

• ./gradlew :grails-datamapping-core:test (full module suite)
• ./gradlew :grails-datamapping-core:codeStyle :grails-datamapping-core:codenarcMain :grails-datamapping-core:codenarcTest
• New specs directly verify the AstPropertyResolveUtils cache-corruption fix, including under concurrent access

🤖 Generated with Claude Code

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[codecov]

Codecov Report

❌ Patch coverage is 82.85714% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.4265%. Comparing base (75cd618) to head (1720abd).

Files with missing lines	Patch %	Lines
...astore/gorm/transform/AstPropertyResolveUtils.java	80.9524%	0 Missing and 4 partials ⚠️
...orm/transform/AbstractGormASTTransformation.groovy	85.7143%	0 Missing and 1 partial ⚠️
...form/AbstractMethodDecoratingTransformation.groovy	50.0000%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                Coverage Diff                 @@
##                8.1.x     #16166        +/-   ##
==================================================
+ Coverage     53.4149%   53.4265%   +0.0116%     
- Complexity      19459      19469        +10     
==================================================
  Files            2081       2081                
  Lines           98993      98994         +1     
  Branches        17361      17359         -2     
==================================================
+ Hits            52877      52889        +12     
+ Misses          38566      38560         -6     
+ Partials         7550       7545         -5     

Files with missing lines	Coverage Δ
...ansactions/transform/TransactionalTransform.groovy	92.5000% <100.0000%> (ø)
...ractDatastoreMethodDecoratingTransformation.groovy	92.2078% <100.0000%> (+2.4642%)	⬆️
.../AbstractTraitApplyingGormASTTransformation.groovy	88.0952% <ø> (ø)
...re/gorm/transform/OrderedGormTransformation.groovy	88.8889% <100.0000%> (ø)
...orm/transform/AbstractGormASTTransformation.groovy	83.3333% <85.7143%> (+4.7619%)	⬆️
...form/AbstractMethodDecoratingTransformation.groovy	91.9355% <50.0000%> (+2.3355%)	⬆️
...astore/gorm/transform/AstPropertyResolveUtils.java	80.7229% <80.9524%> (-1.4200%)	⬇️

... and 4 files with indirect coverage changes

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[testlens-app]

✅ All tests passed ✅

🏷️ Commit: 1720abd
▶️ Tests: 63691 executed
⚪️ Checks: 77/77 completed

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