🦺 [#4057] Do not validate business logic during registration

Discussed with the team on Slack, extensive input validation
where relations between configuration aspects are verified
for consistency and integrity is required, but only during
configuration of the form.

At registration time itself, only the validations that don't
touch external services are performed, so that:

* tests are simpler to write without having to set up mocks
  or VCR, distracting from the actual tested behaviour
* performance during registration is not affected because
  of additional IO. A validation error on this aspect
  would manifest as a runtime error anyway, which is the
  same outcome as the remote API not accepting the
  configured options.

src/openforms/registrations/contrib/zgw_apis/options.py

@@ -123,6 +123,10 @@ def validate(self, attrs: dict[str, Any]) -> dict[str, Any]:
         # We know it exists thanks to the previous check
         group_config = ZGWRegistration.get_zgw_config(attrs)
 
+        validate_business_logic = self.context.get("validate_business_logic", True)
+        if not validate_business_logic:
+            return attrs
+
         # Run all validations against catalogi API in the same connection pool.
         with get_catalogi_client(group_config) as client:
             catalogi = client.get_all_catalogi()
@@ -183,22 +187,19 @@ def validate(self, attrs: dict[str, Any]) -> dict[str, Any]:
                         {"property_mappings": errors}, code="invalid"
                     )
 
-            if not ("medewerker_roltype" in attrs):
-                return attrs
-
-            roltypen = client.list_roltypen(
-                zaaktype=attrs["zaaktype"],
-                matcher=omschrijving_matcher(attrs["medewerker_roltype"]),
-            )
-
-        if not roltypen:
-            raise serializers.ValidationError(
-                {
-                    "medewerker_roltype": _(
-                        "Could not find a roltype with this description related to the zaaktype."
+            if "medewerker_roltype" in attrs:
+                roltypen = client.list_roltypen(
+                    zaaktype=attrs["zaaktype"],
+                    matcher=omschrijving_matcher(attrs["medewerker_roltype"]),
+                )
+                if not roltypen:
+                    raise serializers.ValidationError(
+                        {
+                            "medewerker_roltype": _(
+                                "Could not find a roltype with this description related to the zaaktype."
+                            )
+                        },
+                        code="invalid",
                     )
-                },
-                code="invalid",
-            )
 
         return attrs

src/openforms/registrations/tasks.py

@@ -52,7 +52,8 @@ def pre_registration(submission_id: int, event: PostSubmissionEvents) -> None:
             return
 
         options_serializer = registration_plugin.configuration_options(
-            data=submission.registration_backend.options
+            data=submission.registration_backend.options,
+            context={"validate_business_logic": False},
         )
 
         try:
@@ -229,7 +230,10 @@ def register_submission(submission_id: int, event: PostSubmissionEvents | str) -
         return
 
     logger.debug("De-serializing the plugin configuration options")
-    options_serializer = plugin.configuration_options(data=backend_config.options)
+    options_serializer = plugin.configuration_options(
+        data=backend_config.options,
+        context={"validate_business_logic": False},
+    )
 
     try:
         options_serializer.is_valid(raise_exception=True)