Clean gradle scripts

buildSrc/src/main/kotlin/be/simplenotes/junit-convention.gradle.kts

@@ -0,0 +1,14 @@
+package be.simplenotes
+
+plugins {
+    java apply false
+}
+
+tasks.withType<Test> {
+    useJUnitPlatform()
+}
+
+sourceSets {
+    val test by getting
+    test.resources.srcDir("${rootProject.projectDir}/simplenotes-test-resources/src/test/resources")
+}