schema mapping for api

[jpfinne]

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Summary by cubic

Fixes missing imports for schema-mapped parameter types in API generation, ensuring importMapping is honored when using --schema-mappings (fixes #24232).

• Bug Fixes
  • In DefaultCodegen.fromOperation, add mapped parameter dataType tokens to op.imports when present in importMapping, so the correct fully qualified imports are emitted.
  • Added a Spring test and OpenAPI fixture to verify imports of org.myorg.MyCustomId and org.myorg.MyCustomKey are generated in SomeApi.java and Dummy.java.

^{Written for commit a5c2798. Summary will update on new commits.}