[BUG][kotlin-client] Vertx API: Bad enum class name for default parameters

[okarmazin]

Bug Report Checklist

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

The Vert.x API mustache template does not handle enum class name construction for default values of operation parameters.

It currently outputs {{{defaultValue}}} which does not contain properly constructed class name, leading to invalid code.

It should be {{#isEnum}}{{enumName}}{{operationIdCamelCase}}.{{enumDefaultValue}}{{/isEnum}}{{^isEnum}}{{{defaultValue}}}{{/isEnum}} as in every other client API template.

openapi-generator version

master, bug discovered by accident while fixing a different issue.

I'll fix this.