[gradle plugin] GraphQL extension cannot be used from Groovy scripts

[dariuszkuc]

Library Version
4.0.0-alpha.4

Describe the bug
GraphQLPluginExtension is using Kotlin lambdas for configuration which makes it unusable from Groovy build files. We should use Gradle Action instead of lambdas - i.e. instead of GraphQLPluginClientExtension.() -> Unit use Action<GraphQLPluginClientExtension>

To Reproduce
Apply graphql extension in build.gradle

graphql {
    client {
        endpoint = "http://localhost:8080/graphql"
        packageName = "com.example"
        clientType = GraphQLClientType.KTOR
    }
}

Expected behavior
GraphQL extension DSL can be used from both Groovy and Kotlin scripts.

Workaround
Instead of extension we can configure tasks explicitly

tasks.getByName("graphqlIntrospectSchema") {
    endpoint.set("http://localhost:8080/graphql")
}
tasks.getByName("graphqlGenerateClient") {
    packageName.set("com.example")
    clientType.set(com.expediagroup.graphql.plugin.generator.GraphQLClientType.KTOR)
    schemaFile.set(graphqlIntrospectSchema.outputFile)
    dependsOn("graphqlIntrospectSchema")
}

[dariuszkuc]

When working on this issue we should also update our documentation with samples for both Kotlin and Groovy based build files.