[BUG][DIO] Enum names string are not recognized

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

An enum schema on my swagger.json has a property of x-enumNames but the dart generator appears to not be able to recognize it.
I'm aware that its possible to use x-enum-varnames instead but I don't have a way to easily update the schema yet, and would like to know if its possible to access x-enumNames instead? is it possible to get this value by mustache templates?

openapi-generator version

7.3.0

OpenAPI declaration file content or url

Generation Details

using openapi-generator-cli via npm / npx.

Steps to reproduce

run the openapi-generator-cli generate command via npm and pointing it the swagger schema.

Related issues/PRs

Suggest a fix

none, except for updating the api schema.

Start with the Dart generator and the openapi-generator-cli generate command using the supplied swagger schema. Trace how the enum schema's x-enumNames property is handled and compare the generated Dart enum with the schema. Done means the generator recognizes the enum names, or the supported limitation is clearly established.