Add explicit info about receiver ID=domain in PIX Feed/PDQ Query

docs/faq.md

@@ -47,10 +47,12 @@ end (warning: empty request) and an http error 500 is returned, see xop:include
 This is a data problem. Multiple local patients were either automatically or manually merged into the same master
 patient.
 
-### ITI-45: No Patient data returned
+### ITI-45/ITI-47: No Patient data returned
 
 Verify that the receiver id in the hl7 v3 message contains the oid for the integration system (
-2.16.756.5.30.1.191.1.0.12.1.101.2);
+2.16.756.5.30.1.191.1.0.12.1.101.2).
+You can also try to change the receiver OID to a random OID; if the patient data is returned, then someone fed a bad
+identifier to the patient and CARA needs to clean it manually.
 
 ### IdP HIN ID
 

docs/primarysystems-epr.md

@@ -87,6 +87,12 @@ in the MPI. You need to provide creationTime, sender OID and receiver OID in add
 EPR-SPID, MPI-ID) in the request. For the communication you need a client certificate, but with EPRIK a client
 certificate is not necessary.
 
+
+!!! danger
+
+    Never feed a patient identifier with a domain that is not yours, and especially a domain equal to the configured
+    receiver OID of the plateform. It would make the patient unreachable from PDQ queries.
+
 ### 3.2 Query MPI-PID and EPR-SPID based on local ID
 
 The primary systems needs to query the master patient ID (MPI-ID) for patients to retrieve or provide documents for,