Add attended transfer via remote Contact URI (xferReplacesContact) - closes #237

Regenerate native libs + pjsua2 SWIG bindings from pjsip-android-builder 3.1.0, which adds Call::xferReplacesContact() (Call.java / Call_xferReplacesContact JNI). The variant builds the REFER/Replaces target from the destination dialog's remote Contact URI instead of its AOR, falling back to the AOR when no Contact is present. This keeps attended transfers reachable when the registration binding changes mid-call (network switch / NAT rebind) or behind stricter proxies.

Surface it through the SipService API:
- New PARAM_USE_CONTACT_URI intent extra.
- attendedTransferCall(..., useContactUri) overload; the existing 4-arg overload is unchanged and keeps using the AOR (xferReplaces).
- SipService dispatches to xferReplacesContact() when the flag is set.

Author: aenonGit

sipservice/src/main/java/net/gotev/sipservice/SipService.java

@@ -446,8 +446,15 @@ private void handleAttendedTransferCall(Intent intent) {
             SipCall sipCallOrig = getCall(accountID, callIdOrig);
             if (sipCallOrig != null) {
                 int callIdDest = intent.getIntExtra(PARAM_CALL_ID_DEST, 0);
+                boolean useContactUri = intent.getBooleanExtra(PARAM_USE_CONTACT_URI, false);
                 SipCall sipCallDest = getCall(accountID, callIdDest);
-                sipCallOrig.xferReplaces(sipCallDest, new CallOpParam());
+                Logger.debug(TAG, "Completing attended transfer (useContactUri=" + useContactUri + ")");
+                // Target the remote Contact URI when requested; otherwise the AOR.
+                if (useContactUri) {
+                    sipCallOrig.xferReplacesContact(sipCallDest, new CallOpParam());
+                } else {
+                    sipCallOrig.xferReplaces(sipCallDest, new CallOpParam());
+                }
             }
         } catch (Exception exc) {
             Logger.error(TAG, "Error while finalizing attended transfer", exc);

sipservice/src/main/java/net/gotev/sipservice/SipServiceCommand.java

@@ -399,13 +399,24 @@ public static void transferCall(Context context, String accountID, int callID, S
      * @param callIdDest call ID of the destination call
      */
     public static void attendedTransferCall(Context context, String accountID, int callIdOrig, int callIdDest) {
+        attendedTransferCall(context, accountID, callIdOrig, callIdDest, false);
+    }
+
+    /**
+     * Attended call transfer, selecting how the destination dialog is targeted.
+     * @param useContactUri when true, completes via the remote Contact URI (xferReplacesContact)
+     *                      instead of the AOR (xferReplaces), falling back to the AOR if the
+     *                      Contact URI is unavailable.
+     */
+    public static void attendedTransferCall(Context context, String accountID, int callIdOrig, int callIdDest, boolean useContactUri) {
         checkAccount(accountID);
 
         Intent intent = new Intent(context, SipService.class);
         intent.setAction(ACTION_ATTENDED_TRANSFER_CALL);
         intent.putExtra(PARAM_ACCOUNT_ID, accountID);
         intent.putExtra(PARAM_CALL_ID, callIdOrig);
         intent.putExtra(PARAM_CALL_ID_DEST, callIdDest);
+        intent.putExtra(PARAM_USE_CONTACT_URI, useContactUri);
         context.startService(intent);
     }