convert MAC to interface

src/commonMain/kotlin/com/infendro/mac/HMAC.kt

@@ -5,7 +5,7 @@ import com.infendro.hash.HashFunction
 
 class HMAC(
     val function: HashFunction,
-) : MAC() {
+) : MAC {
     override val bytes: Int
         get() = function.bytes
 

src/commonMain/kotlin/com/infendro/mac/MAC.kt

@@ -1,11 +1,11 @@
 package com.infendro.mac
 
-abstract class MAC {
-    abstract val bytes: Int
+interface MAC {
+    val bytes: Int
     val bits: Int
         get() = bytes * 8
 
-    abstract fun hash(
+    fun hash(
         key: UByteArray,
         value: UByteArray,
     ): UByteArray