Release v4.14.0

- Implemented `ReferrerMainCenterAggregatorTest` to validate data transformation and query logic.
- Added data providers and query builders to ensure comprehensive test coverage.
- Verified correct handling of rolling dates and aggregator logic.

.changes/unreleased/Feature-20251230-164303.yaml

@@ -1,6 +0,0 @@
-kind: Feature
-body: Add filter and aggregator based on referrer's main center for exports of accompanying period
-time: 2025-12-30T16:43:03.898677616+01:00
-custom:
-    Issue: "486"
-    SchemaChange: No schema change

.changes/unreleased/Fixed-20260223-182212.yaml

@@ -1,7 +0,0 @@
-kind: Fixed
-body: 'Fix import of postal code: mark postal code as deleted if they are not present in the import any more'
-time: 2026-02-23T18:22:12.92214987+01:00
-custom:
-    Issue: "502"
-    MR: "968"
-    SchemaChange: No schema change

.changes/unreleased/Fixed-20260309-101721.yaml

@@ -1,7 +0,0 @@
-kind: Fixed
-body: Add a flash message when reassigning accompanying course (reassign list)
-time: 2026-03-09T10:17:21.923487588+01:00
-custom:
-    Issue: "503"
-    MR: "969"
-    SchemaChange: No schema change