Fixes https://github.com/spring-projects/spring-integration/issues/3428 The Kotlin Gradle plugin starting with Kotlin `1.4` adds a standard Kotlin lib into `compile` scope fully ignoring an `optional` variant. See more info here: https://kotlinlang.org/docs/reference/using-gradle.html#dependency-on-the-standard-library * Add `kotlin.stdlib.default.dependency=false` into `gradle.properties` to rely only on the explicit dependency definitions in the project config * Remove explicit Kotlin deps from test scope in the target modules since it is declared globally for all the modules * Fix author emails in the `publish-maven.gradle` to their VMware variants * Remove usage of `org.jetbrains.annotations` in favor of `@Nullable` from Spring Framework