Add support for XEP-0418: DNS Queries over XMPP (DoX)

Fixes SMACK-862.

smack-resolver-minidns-dox/build.gradle

@@ -0,0 +1,7 @@
+description = """\
+DNS over XMPP (DoX) support using MiniDNS."""
+
+dependencies {
+	compile project(path: ':smack-resolver-minidns')
+	compile project(path: ':smack-experimental')
+}

smack-resolver-minidns-dox/src/main/java/org/jivesoftware/smackx/dox/resolver/minidns/DnsOverXmppMiniDnsResolver.java

@@ -0,0 +1,47 @@
+/**
+ *
+ * Copyright 2019 Florian Schmaus
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jivesoftware.smackx.dox.resolver.minidns;
+
+import java.io.IOException;
+
+import org.jivesoftware.smackx.dox.DnsOverXmppResolver;
+
+import org.minidns.DnsClient;
+import org.minidns.dnsmessage.DnsMessage;
+import org.minidns.dnsmessage.Question;
+import org.minidns.dnsqueryresult.DnsQueryResult;
+
+public class DnsOverXmppMiniDnsResolver implements DnsOverXmppResolver {
+
+    public static final DnsOverXmppMiniDnsResolver INSTANCE = new DnsOverXmppMiniDnsResolver(new DnsClient());
+
+    private final DnsClient dnsClient;
+
+    public DnsOverXmppMiniDnsResolver(DnsClient dnsClient) {
+        this.dnsClient = dnsClient;
+    }
+
+    @Override
+    public DnsMessage resolve(DnsMessage query) throws IOException {
+        Question question = query.getQuestion();
+
+        DnsQueryResult dnsQueryResult = dnsClient.query(question);
+
+        return dnsQueryResult.response;
+    }
+
+}

smack-resolver-minidns-dox/src/main/java/org/jivesoftware/smackx/dox/resolver/minidns/package-info.java

@@ -0,0 +1,21 @@
+/**
+ *
+ * Copyright 2019 Florian Schmaus
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * XEP-0418: DNS Queries over XMPP (Dox) using MiniDNS.
+ */
+package org.jivesoftware.smackx.dox.resolver.minidns;