KOP-2139 KOP-2444 setup: Add xta client unit test

src/test/java/de/ozgcloud/xta/client/XtaClientTest.java

+package de.ozgcloud.xta.client;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.apache.commons.lang3.NotImplementedException;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+
+class XtaClientTest {
+
+	@DisplayName("get messages metadata")
+	@Nested
+	class TestGetMessagesMetadata {
+		@DisplayName("should something")
+		@Test
+		void shouldSomething() {
+			var client = createClient();
+
+			assertThrows(NotImplementedException.class, () -> client.getMessagesMetadata("selfIdentifier"));
+		}
+	}
+
+	private XtaClient createClient() {
+		return new XtaClient();
+	}
+
+}
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