use managed objects, allow caching, require less config

src/main/kotlin/com/openosrs/injector/InjectPlugin.kt

@@ -11,17 +11,18 @@ import org.gradle.api.Plugin
 import org.gradle.api.Project
 
 class InjectPlugin: Plugin<Project> {
-    override fun apply(project: Project) {
-        val extension = project.extensions.create("injector", Injextention::class.java, project)
+    override fun apply(project: Project) { with(project) {
+        val task = tasks.create("inject", Inject::class.java)
+        task.output.convention { file("$buildDir/libs/$name-$version.jar") }
 
-        project.tasks.create("inject", Inject::class.java) {
-            it.vanilla.set(extension.vanilla)
-            it.rsclient.set(extension.rsclient)
-            it.mixins.set(extension.mixins)
-            it.rsapi.set(extension.rsapi)
-            if (extension.output.isPresent) {
-                it.output.set(extension.output)
-            }
+        artifacts {
+            it.add("runtimeElements", task.output)
         }
-    }
+
+        tasks.getByName("assemble") {
+            it.finalizedBy("inject")
+        }
+
+        extensions.add(InjectExtension::class.java, "injector", task.extension)
+    }}
 }