#232 Payment document linkage

* adds error message on intervention view if a payment has been added but no document has been uploaded yet
* adds same check to quality checker, meaning no intervention can be recorded which has a payment but no document
* adds trigger for sending data to egon on uploading a document in case of an already existing payment
* adds translations

intervention/utils/quality.py

@@ -21,8 +21,21 @@ class InterventionQualityChecker(AbstractQualityChecker):
         self._check_legal_data()
         self._check_compensations()
         self._check_geometry()
+        self._check_payment_documents()
         self.valid = len(self.messages) == 0
 
+    def _check_payment_documents(self):
+        """ Checks existence of documents in case of payments
+
+        There should be at least one legal document which defines the payment's total amount.
+
+        Returns:
+
+        """
+        has_payment_without_document = self.obj.payments.exists() and not self.obj.get_documents()[1].exists()
+        if has_payment_without_document:
+            self._add_missing_attr_name(_("Documents"))
+
     def _check_responsible_data(self):
         """ Checks data quality of related Responsibility