Add mitigation with task and mapping import

Signed-off-by: gearnode <bryan@frimin.fr>

pkg/coredata/migrations/20250401T144700Z.sql

@@ -0,0 +1,5 @@
+ALTER TABLE tasks ADD COLUMN reference_id TEXT DEFAULT '';
+ALTER TABLE tasks ALTER COLUMN reference_id SET NOT NULL;
+ALTER TABLE tasks ALTER COLUMN reference_id DROP DEFAULT;
+
+ALTER TABLE tasks ADD CONSTRAINT tasks_reference_id_unique UNIQUE (id, reference_id);