OZG-3136 add xta message with file

xta-adapter/src/main/java/de/ozgcloud/eingang/xta/XtaMessage.java

+package de.ozgcloud.eingang.xta;
+
+public record XtaMessage(
+		XtaMessageMetaData metaData,
+		XtaFile messageFile) {
+
+}

xta-adapter/src/main/java/de/ozgcloud/eingang/xta/XtaRemoteService.java

@@ -23,7 +23,7 @@ class XtaRemoteService {
 		return null;
 	}
 
-	public XtaFile getMessageFile(XtaMessageId messageId) {
+	public XtaMessage getMessage(XtaMessageId messageId) {
 		// TODO implement me
 		return null;
 	}