Do not depend on generated classes for update-secret extension

Some CI testing jobs are using the 3.7 branch of codegen, which does not contain
the update-secret extension. The Java client then cannot be built
because it requires some generated code for the extension.

This commit adds the code to handle update-secret and thus
makes the generated code not necessary. This is just a workaround for
these testing jobs to succeed, it does not change the handling of the
update-secret extension in the client.

[#167029587]

References #626

src/main/java/com/rabbitmq/client/impl/AMQConnection.java

@@ -442,7 +442,7 @@ public void start()
                 }
                 String refreshedPassword = credentialsProvider.getPassword();
 
-                AMQImpl.Connection.UpdateSecret updateSecret = new AMQImpl.Connection.UpdateSecret(
+                UpdateSecretExtension.UpdateSecret updateSecret = new UpdateSecretExtension.UpdateSecret(
                         LongStringHelper.asLongString(refreshedPassword), "Refresh scheduled by client"
                 );
                 try {

src/main/java/com/rabbitmq/client/impl/UpdateSecretExtension.java

@@ -0,0 +1,108 @@
+// Copyright (c) 2019 Pivotal Software, Inc.  All rights reserved.
+//
+// This software, the RabbitMQ Java client library, is triple-licensed under the
+// Mozilla Public License 1.1 ("MPL"), the GNU General Public License version 2
+// ("GPL") and the Apache License version 2 ("ASL"). For the MPL, please see
+// LICENSE-MPL-RabbitMQ. For the GPL, please see LICENSE-GPL2.  For the ASL,
+// please see LICENSE-APACHE2.
+//
+// This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND,
+// either express or implied. See the LICENSE file for specific language governing
+// rights and limitations of this software.
+//
+// If you have any questions regarding licensing, please contact us at
+// [email protected].
+
+package com.rabbitmq.client.impl;
+
+import com.rabbitmq.client.LongString;
+
+import java.io.IOException;
+import java.util.Objects;
+
+/**
+ * Helper for <code>update-secret</code> extension {@link com.rabbitmq.client.Method}.
+ * <p>
+ * {@link com.rabbitmq.client.Method} classes are usually automatically
+ * generated, but providing the class directly is necessary in this case
+ * for some internal CI testing jobs running against RabbitMQ 3.7.
+ *
+ * @since 5.8.0
+ */
+abstract class UpdateSecretExtension {
+
+    static class UpdateSecret extends Method {
+
+        private final LongString newSecret;
+        private final String reason;
+
+        public UpdateSecret(LongString newSecret, String reason) {
+            if (newSecret == null)
+                throw new IllegalStateException("Invalid configuration: 'newSecret' must be non-null.");
+            if (reason == null)
+                throw new IllegalStateException("Invalid configuration: 'reason' must be non-null.");
+            this.newSecret = newSecret;
+            this.reason = reason;
+        }
+
+        public String getReason() {
+            return reason;
+        }
+
+        public int protocolClassId() {
+            return 10;
+        }
+
+        public int protocolMethodId() {
+            return 70;
+        }
+
+        public String protocolMethodName() {
+            return "connection.update-secret";
+        }
+
+        public boolean hasContent() {
+            return false;
+        }
+
+        public Object visit(AMQImpl.MethodVisitor visitor) throws IOException {
+            return null;
+        }
+
+
+        @Override
+        public boolean equals(Object o) {
+            if (this == o)
+                return true;
+            if (o == null || getClass() != o.getClass())
+                return false;
+            UpdateSecret that = (UpdateSecret) o;
+            if (!Objects.equals(newSecret, that.newSecret))
+                return false;
+            return Objects.equals(reason, that.reason);
+        }
+
+        @Override
+        public int hashCode() {
+            int result = 0;
+            result = 31 * result + (newSecret != null ? newSecret.hashCode() : 0);
+            result = 31 * result + (reason != null ? reason.hashCode() : 0);
+            return result;
+        }
+
+        public void appendArgumentDebugStringTo(StringBuilder acc) {
+            acc.append("(new-secret=")
+                    .append(this.newSecret)
+                    .append(", reason=")
+                    .append(this.reason)
+                    .append(")");
+        }
+
+        public void writeArgumentsTo(MethodArgumentWriter writer)
+                throws IOException {
+            writer.writeLongstr(this.newSecret);
+            writer.writeShortstr(this.reason);
+        }
+    }
+}
+

src/test/java/com/rabbitmq/client/impl/AMQConnectionRefreshCredentialsTest.java

@@ -66,9 +66,9 @@ public boolean processAsync(Command c) throws IOException {
 
                             @Override
                             public AMQCommand rpc(Method m) throws IOException, ShutdownSignalException {
-                                if (m instanceof AMQImpl.Connection.UpdateSecret) {
+                                if (m instanceof UpdateSecretExtension.UpdateSecret) {
                                     super.rpc(m);
-                                    return super.rpc(new AMQImpl.Connection.UpdateSecret(LongStringHelper.asLongString(""), "Refresh scheduled by client") {
+                                    return super.rpc(new UpdateSecretExtension.UpdateSecret(LongStringHelper.asLongString(""), "Refresh scheduled by client") {
                                         @Override
                                         public int protocolMethodId() {
                                             return 255;