fixed merge register assign operation

Author: mweberUKL

src/main/java/eu/antidotedb/client/MergeRegisterKey.java

@@ -3,6 +3,7 @@
 import com.google.protobuf.ByteString;
 import eu.antidotedb.antidotepb.AntidotePB;
 
+import javax.annotation.CheckReturnValue;
 import java.util.List;
 
 public class MergeRegisterKey<V> extends Key<V> {
@@ -23,4 +24,14 @@ public interface ValueMerger<V> {
     V readResponseToValue(AntidotePB.ApbReadObjectResp resp) {
         return merger.merge(ResponseDecoder.multiValueRegister(format).readResponseToValue(resp));
     }
+
+    /**
+     * Creates an update operation which assigns a new value to the register.
+     * <p>
+     * Use the methods on {@link Bucket} to execute the update.
+     */
+    @CheckReturnValue
+    public UpdateOpDefaultImpl assign(V value) {
+        return RegisterKey.buildRegisterUpdate(this, format.encode(value));
+    }
 }