fix: missing overlays, outdated inputs in java/kotlin

[nartsisss]

Depends on #53
Fixes #55

[vbrandl]

I think since NixOS/nixpkgs@ea0bc32 overriding jre for the maven package is not possible and causes the evaluation to fail with

error: function 'anonymous lambda' called with unexpected argument 'jre'

So the line maven = prev.maven.override { jre = jdk; }; has to be replaced with maven = prev.maven.override { jdk_headless = jdk; };

[hatch01]

Seems fine. And important, to have the right jdk

[lucperkins]

Sorry for the delay. Somehow I didn't get the notification for this. LGTM!