feat(x2/last): return PDU raw b64 encoded

The ObjectMapper is not smart enough to translate that object, so we
intend to use our own decoder for that.

src/main/java/com/sipgate/li/simulator/controller/X2Controller.java

@@ -2,6 +2,10 @@
 
 import com.sipgate.li.lib.x2x3.PduObject;
 import com.sipgate.li.simulator.x2x3.X2X3Memory;
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.Base64;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -18,10 +22,15 @@ public X2Controller(final X2X3Memory x2X3Memory) {
   }
 
   @GetMapping("/last")
-  public ResponseEntity<PduObject> getLast() {
+  public ResponseEntity<String> getLast() throws IOException {
     if (x2X3Memory.getLast() == null) {
       return ResponseEntity.notFound().build();
     }
-    return ResponseEntity.ok(x2X3Memory.getLast());
+
+    final var pduBytes = new ByteArrayOutputStream();
+    final var pduStream = new DataOutputStream(pduBytes);
+    x2X3Memory.getLast().writeTo(pduStream);
+
+    return ResponseEntity.ok(Base64.getEncoder().encodeToString(pduBytes.toByteArray()));
   }
 }

src/test/java/com/sipgate/li/simulator/e2e/InterceptsX2Test.java

@@ -3,6 +3,9 @@
 import static org.assertj.core.api.Assertions.assertThat;
 
 import com.sipgate.li.lib.x2x3.*;
+import io.netty.buffer.Unpooled;
+import java.util.ArrayList;
+import java.util.Base64;
 import org.junit.jupiter.api.Tag;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
@@ -20,7 +23,12 @@ void simulator_receives_x2(final SimulatorClient simulatorClient) throws Excepti
     simulatorClient.post("/sip", "application/octet-stream", body, Void.class, 204);
 
     // THEN
-    final PduObject result = simulatorClient.get("/x2/last", PduObject.class);
+    final var base64edByteStreamOfAPduObject = simulatorClient.get("/x2/last", String.class);
+    final var decoded = Unpooled.wrappedBuffer(Base64.getDecoder().decode(base64edByteStreamOfAPduObject));
+    final var outList = new ArrayList<>();
+    new X2X3Decoder(Integer.MAX_VALUE, Integer.MAX_VALUE).decode(decoded, outList);
+
+    final PduObject result = (PduObject) outList.get(0);
     assertThat(result).isNotNull();
     assertThat(result.pduType()).isEqualTo(PduType.X2_PDU);
     assertThat(result.payloadFormat()).isEqualTo(PayloadFormat.SIP);