Base64 encode and validated decode helpers

import java.util.Base64

fun encode(value: String): String =
    Base64.getEncoder().encodeToString(value.toByteArray(Charsets.UTF_8))

fun decode(encoded: String): String? =
    try {
        String(Base64.getDecoder().decode(encoded), Charsets.UTF_8)
    } catch (e: IllegalArgumentException) {
        null
    }

check(decode(encode("héllo BITS")) == "héllo BITS")
check(decode("not base64!") == null)