Spring Security Ensure Kotlin 1.3 compatibility

While we upgrade our Kotlin dependency to 1.5.x, we should ensure that we retain Kotlin 1.3 compatibility, so that users can continue to use Kotlin 1.3 and still upgrade to the latest version of Spring Security.

kotlinOptions {
    languageVersion = "1.3"
    apiVersion = "1.3"
    freeCompilerArgs = ["-Xjsr305=strict", "-Xsuppress-version-warnings"]
    allWarningsAsErrors = true
}