Use the canonical constructor when mapping Java record inputs

[auraseb]

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Pull Request type

• Bugfix
• Feature
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Changes in this PR

DefaultInputObjectMapper.handleRecordClass used declaredConstructors.first() to build a record. The order of getDeclaredConstructors() is unspecified, and when a record declares a convenience constructor HotSpot returns that one first, so mapping failed with IllegalArgumentException: wrong number of arguments.

The mapper now looks up the canonical constructor by the record component types, which is how the canonical constructor is defined by the JLS.

Tests added in InputObjectMapperTest:

• a plain record (RecordInput, which existed as a fixture but was not used by any test)
• a record with an additional constructor (RecordInputWithSecondaryConstructor), which fails on master and passes with this change

Issue #

Alternatives considered

Filtering declaredConstructors by parameter count. That still picks the wrong constructor when a second constructor has the same arity, so looking it up by component types is the precise option.

Fixes #2360