[1.0.x] Fix nested Redis hash map conversion

[sagile]

Summary

• Backports fix: MappingException for Map<String,Object> fields with nested maps in @RedisHash (gh-755) #757 to 1.0.x so @RedisHash entities can persist and reload Map<String, Object> values containing nested maps and collections.
• Keeps Redis OM built-in custom converters registered when callers provide additional custom conversions.

Validation

• Fail-first check: with only the new tests on the 1.0.x baseline, ./gradlew :tests:test --tests "com.redis.om.spring.repository.HashWithNestedMapTest" --tests "com.redis.om.spring.convert.RedisOMCustomConversionsTest" failed 5 tests covering custom converter registration and nested map/list round trips.
• ./gradlew :tests:test --tests "com.redis.om.spring.repository.HashWithNestedMapTest" --tests "com.redis.om.spring.convert.RedisOMCustomConversionsTest"
• ./gradlew :demos:roms-hashes:test --tests "com.redis.om.hashes.RomsHashesApplicationTests"
• ./gradlew spotlessApply
• ./gradlew spotlessCheck build aggregateTestReport -S

CI Notes

• Reviewed .github/workflows/build.yml: PR jobs run spotlessCheck -S, assemble -S, sharded :tests:test -S, and :demos:build -S.
• Local full validation covered the same formatting, build, tests, demos, and aggregate report surfaces via spotlessCheck build aggregateTestReport -S.

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Note

Medium Risk
Changes core Redis OM serialization in MappingRedisOMConverter for all hash map/list fields; behavior is well covered by round-trip tests but affects a sensitive persistence path.

Overview
Fixes gh-755 so @RedisHash entities can save and reload Map<String, Object> / List<Object> fields when values are nested maps or collections (e.g. Jackson LinkedHashMap / ArrayList), which previously failed with MappingException on Spring Data Commons 3.2.4+.

MappingRedisOMConverter now treats nested Map and Collection values in writeInternal before getRequiredPersistentEntity(), and reloads map/collection entries via readNestedValue (including heuristic map vs list when the value type is Object). readMapOfSimpleTypes uses full key discovery and the entity class for nested reads.

RedisOMCustomConversions merges caller-supplied converters with built-ins instead of replacing them.

Regression coverage: HashWithNestedMapTest, RedisOMCustomConversionsTest, demo User.metadata and RomsHashesApplicationTests (Testcontainers).

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[jit-ci]

🛡️ Jit Security Scan Results

✅ No security findings were detected in this PR

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^{Security scan by Jit}