Make the Gradle Kotlin DSL the default

[graemerocher]

We should make the Gradle Kotlin DSL the default because:

a. It is now the default in Gradle
b. It doesn't break for each release of the JDK
c. It provides a better IDE experience

[sdelamo]

what do you mean by this?

It doesn't break for each release of the JDK

[graemerocher]

The Groovy DSL depends on Groovy which has to be upgraded for each JDK release otherwise you get an error like

startup failed:
General error during conversion: Unsupported class file major version 61

java.lang.IllegalArgumentException: Unsupported class file major version 61
	at groovyjarjarasm.asm.ClassReader.<init>(ClassReader.java:196)
	at groovyjarjarasm.asm.ClassReader.<init>(ClassReader.java:177)
	at groovyjarjarasm.asm.ClassReader.<init>(ClassReader.java:163)
	at groovyjarjarasm.asm.ClassReader.<init>(ClassReader.java:284)
	at org.codehaus.groovy.ast.decompiled.AsmDecompiler.parseClass(AsmDecompiler.java:81)
	at org.codehaus.groovy.control.ClassNodeResolver.findDecompiled(ClassNodeResolver.java:251)

Given that Groovy releases take a while and Gradle takes a while to upgrade to new Groovy release it means that Gradle with Groovy is broken out the box on the day a new JDK comes out and you have to wait until the next version.

[timyates]

Raised #2080 for Micronaut 4.2.0