[REQ] Option to automatically delete all files/folders in outputDir for openapi gradle plugin

Created by: s101d1

For openapi-generator-gradle-plugin, could you add option to automatically delete all files and folders in outputDir before generating the code files?

The option can be called "cleanOputputDir" (boolean) or such.

openApiGenerate {
    generatorName = "kotlin"
    inputSpec = "$rootDir/specs/petstore-v3.0.yaml".toString()
    outputDir = "$buildDir/generated".toString()
    apiPackage = "org.openapi.example.api"
    invokerPackage = "org.openapi.example.invoker"
    modelPackage = "org.openapi.example.model"
    modelFilesConstrainedTo = [
            "Error"
    ]
    configOptions = [
        dateLibrary: "java8"
    ]
    cleanOutputDir = true
}