Add tests for duplicated operationId

[wing328]

add a test https://github.com/OpenAPITools/openapi-generator/pull/20070/files#diff-73bab52f5d7424b5d166fb81aa39bfe47a4019ad4b9eb207b05a01c449d0c9b5R3157 for duplicated operationId

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