[Java] ensure JsonTypeName not generated for class implementing oneOf with discriminator

[jpfinne]

Fixes #23997

For a child that's part of a non-empty discriminator mapping, the parent interface already declares the type id via @JsonSubTypes.Type(name = ...), so emitting @JsonTypeName on the child is redundant (and was the source of the original mismatch). Marking the mapped child models with hasDiscriminatorWithNonEmptyMapping so the existing {{^hasDiscriminatorWithNonEmptyMapping}} guard suppresses @JsonTypeName

The fix applies for all generators using Jackson and CodegenModel.hasDiscriminatorWithNonEmptyMapping

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Summary by cubic

Stop generating @JsonTypeName for child models when a parent oneOf interface uses a discriminator with a non-empty mapping. This removes redundant annotations and avoids type id mismatches with the parent’s @JsonSubTypes and @JsonTypeInfo.

• Bug Fixes
  • In DefaultCodegen, mark mapped child models with hasDiscriminatorWithNonEmptyMapping (with null-safe handling) so templates skip emitting @JsonTypeName across Jackson-based generators.
  • Expanded issue24003 Spring test and issue_24003.yaml to assert the parent interface has @JsonTypeInfo (including visible = true) and @JsonSubTypes, and child classes do not contain @JsonTypeName.

^{Written for commit dc0d05b. Summary will update on new commits.}

[cubic-dev-ai]

2 issues found across 3 files

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