FDP-3254: Open SigningUtil.kt and make the keyProvider accessible (#92)

Author: JelleHoffman

oslp-message-signing/src/main/kotlin/com/gxf/utilities/oslp/message/signing/SigningUtil.kt

@@ -8,7 +8,7 @@ import io.github.oshai.kotlinlogging.KotlinLogging
 import java.security.SecureRandom
 import java.security.Signature
 
-class SigningUtil(val signingConfiguration: SigningProperties, private val keyProvider: KeyProvider) {
+open class SigningUtil(val signingConfiguration: SigningProperties, val keyProvider: KeyProvider) {
     private val logger = KotlinLogging.logger {}
 
     fun createSignature(message: ByteArray): ByteArray {