feat: add username resignation builder

src/main/java/org/arkecosystem/crypto/transactions/Deserializer.java

@@ -108,6 +108,8 @@ private AbstractTransaction guessTransactionFromTransactionData(
             return new ValidatorResignation(transactionData.toHashMap());
         } else if (TransactionTypeIdentifier.isUsernameRegistration(payload)) {
             return new UsernameRegistration(transactionData.toHashMap());
+        } else if (TransactionTypeIdentifier.isUsernameResignation(payload)) {
+            return new UsernameResignation(transactionData.toHashMap());
         }
 
         return new EvmCall();

src/main/java/org/arkecosystem/crypto/transactions/builder/UsernameResignationBuilder.java

@@ -0,0 +1,24 @@
+package org.arkecosystem.crypto.transactions.builder;
+
+import org.arkecosystem.crypto.enums.ContractAddresses;
+import org.arkecosystem.crypto.transactions.types.AbstractTransaction;
+import org.arkecosystem.crypto.transactions.types.UsernameResignation;
+
+public class UsernameResignationBuilder
+        extends AbstractTransactionBuilder<UsernameResignationBuilder> {
+
+    public UsernameResignationBuilder() {
+        super();
+        this.transaction.recipientAddress = ContractAddresses.USERNAMES.address();
+    }
+
+    @Override
+    protected AbstractTransaction getTransactionInstance() {
+        return new UsernameResignation();
+    }
+
+    @Override
+    protected UsernameResignationBuilder instance() {
+        return this;
+    }
+}

src/main/java/org/arkecosystem/crypto/transactions/types/UsernameResignation.java

@@ -0,0 +1,27 @@
+package org.arkecosystem.crypto.transactions.types;
+
+import java.util.Map;
+import org.arkecosystem.crypto.enums.AbiFunction;
+import org.arkecosystem.crypto.enums.ContractAbiType;
+import org.arkecosystem.crypto.utils.AbiEncoder;
+
+public class UsernameResignation extends AbstractTransaction {
+
+    public UsernameResignation() {
+        super();
+    }
+
+    public UsernameResignation(Map<String, Object> data) {
+        super(data);
+    }
+
+    @Override
+    public String getPayload() {
+        try {
+            return new AbiEncoder(ContractAbiType.USERNAMES)
+                    .encodeFunctionCall(AbiFunction.USERNAME_RESIGNATION.toString());
+        } catch (Exception e) {
+            throw new RuntimeException("Error encoding username resignation call", e);
+        }
+    }
+}

src/test/java/org/arkecosystem/crypto/transactions/builder/UsernameResignationBuilderTest.java

@@ -0,0 +1,69 @@
+package org.arkecosystem.crypto.transactions.builder;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.arkecosystem.crypto.AbstractTest;
+import org.arkecosystem.crypto.encoding.Hex;
+import org.arkecosystem.crypto.enums.ContractAddresses;
+import org.arkecosystem.crypto.transactions.Deserializer;
+import org.arkecosystem.crypto.transactions.types.AbstractTransaction;
+import org.arkecosystem.crypto.transactions.types.UsernameResignation;
+import org.junit.jupiter.api.Test;
+
+public class UsernameResignationBuilderTest extends AbstractTest {
+
+    private static final String RESIGN_SELECTOR = "0xebed6dab";
+
+    @Test
+    public void it_should_default_to_the_usernames_well_known_contract() {
+        UsernameResignationBuilder builder = new UsernameResignationBuilder();
+
+        assertEquals(ContractAddresses.USERNAMES.address(), builder.transaction.recipientAddress);
+    }
+
+    @Test
+    public void it_should_encode_resign_username_selector() {
+        UsernameResignationBuilder builder =
+                new UsernameResignationBuilder()
+                        .gasPrice(5_000_000_000L)
+                        .gasLimit(100_000)
+                        .nonce(1L);
+
+        builder.transaction.refreshPayloadData();
+
+        assertEquals(RESIGN_SELECTOR, builder.transaction.data);
+    }
+
+    @Test
+    public void it_should_sign_and_verify_a_username_resignation_transaction() {
+        UsernameResignationBuilder builder =
+                new UsernameResignationBuilder()
+                        .gasPrice(5_000_000_000L)
+                        .gasLimit(100_000)
+                        .nonce(1L)
+                        .sign(this.passphrase);
+
+        assertNotNull(builder.transaction.signature);
+        assertNotNull(builder.transaction.id);
+        assertTrue(builder.verify());
+    }
+
+    @Test
+    public void it_should_round_trip_through_serialization() {
+        UsernameResignationBuilder builder =
+                new UsernameResignationBuilder()
+                        .gasPrice(5_000_000_000L)
+                        .gasLimit(100_000)
+                        .nonce(7L)
+                        .sign(this.passphrase);
+
+        String serialized = Hex.encode(builder.transaction.serialize());
+        AbstractTransaction restored = Deserializer.newDeserializer(serialized).deserialize();
+
+        assertInstanceOf(UsernameResignation.class, restored);
+        assertEquals(builder.transaction.id, restored.id);
+        assertEquals(
+                builder.transaction.recipientAddress.toLowerCase(),
+                restored.recipientAddress.toLowerCase());
+    }
+}