add validation for new contact of duplicate entries

entity/Contact_entity/Contact_entity.aod

@@ -4,6 +4,7 @@
   <title>Contact</title>
   <majorModelMode>DISTRIBUTED</majorModelMode>
   <documentation>%aditoprj%/entity/Contact_entity/documentation.adoc</documentation>
+  <onValidation>%aditoprj%/entity/Contact_entity/onValidation.js</onValidation>
   <iconId>VAADIN:USERS</iconId>
   <recordContainer>db</recordContainer>
   <entityFields>
@@ -19,6 +20,7 @@
       <consumer>Organisations</consumer>
       <mandatory v="true" />
       <displayValueProcess>%aditoprj%/entity/Contact_entity/entityfields/organisation_id/displayValueProcess.js</displayValueProcess>
+      <onValidation>%aditoprj%/entity/Contact_entity/entityfields/organisation_id/onValidation.js</onValidation>
       <onValueChange>%aditoprj%/entity/Contact_entity/entityfields/organisation_id/onValueChange.js</onValueChange>
     </entityField>
     <entityField>

entity/Contact_entity/entityfields/organisation_id/onValidation.js

+import("system.translate");
+import("system.result");
+import("system.db");
+import("system.vars");
+import("Entity_lib");
+import("Sql_lib");
+
+var personId = vars.get("$field.PERSON_ID");
+var organisationId = ProcessHandlingUtils.getOnValidationValue("$field.ORGANISATION_ID");
+
+if (personId && organisationId)
+{    
+    var alreadyExistantContactId = db.cell(SqlCondition.begin()
+                                                       .andPrepare("CONTACT.PERSON_ID", personId)
+                                                       .andPrepare("CONTACT.ORGANISATION_ID", organisationId)
+                                                       .buildSql("select CONTACT.CONTACTID from CONTACT"));
+    if (alreadyExistantContactId != "")
+        result.string(translate.text("The combination of person and organisation does already exist and can not be created once more."));
+}
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