[BUG][Kotlin] Enum type name starts lowecased and causes a build-error

[hrach]

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

After updating to 7.6.0 (from 7.4.0) there is a regression. The produced code does not compile:

data class FavoritesEndpointItemsDto constructor (
    @Json(name = "user_gender")
    val userGender: FavoritesEndpointItemsDto.UserGender? = null,
) {
    /**
     * 
     *
     * Values: MALE,FEMALE
     */
    enum class userGender(val value: kotlin.String) {
        @Json(name = "male") MALE("male"),
        @Json(name = "female") FEMALE("female");
    }
}

openapi-generator version

7.6.0, yes, a regression

OpenAPI declaration file content or url

            "FavoritesEndpoint_Items": {
                "type": "object",
                "properties": {
                    "user_gender": {
                        "type": "string",
                        "enum": [
                            "male",
                            "female"
                        ]
                    }
                },
                "required": [
                ]
            },

Related issues/PRs

[hrach]

Tested 7.5.0, it is broken as well, so it is in its changes.