Fix unfollow on multiple version of article/constitution

src/main/resources/sql/functions/follow/unfollow.sql

@@ -1,12 +1,39 @@
 create or replace function unfollow(reference regclass, _target_id uuid, _created_by_id uuid) returns void
     language plpgsql as
 $$
+declare
+    _targets_ids uuid[];
 begin
-    delete
-    from follow f
-    where f.created_by_id = _created_by_id
-      and f.target_id = _target_id
-      and f.target_reference = reference;
+    if reference = 'article'::regclass then
+        select array_agg(a2.id) into _targets_ids
+        from article a1
+        join article a2 using (version_id)
+        where a1.id = _target_id;
+
+        delete
+        from follow f
+        where f.created_by_id = _created_by_id
+          and f.target_id = any(_targets_ids)
+          and f.target_reference = reference;
+    elseif reference = 'constitution'::regclass then
+        select array_agg(c2.id) into _targets_ids
+        from constitution c1
+        join constitution c2 using (version_id)
+        where c1.id = _target_id;
+        delete
+        from follow f
+        where f.created_by_id = _created_by_id
+          and f.target_id = any(_targets_ids)
+          and f.target_reference = reference;
+    elseif reference = 'citizen'::regclass then
+        delete
+        from follow f
+        where f.created_by_id = _created_by_id
+          and f.target_id = _target_id
+          and f.target_reference = reference;
+    else
+        raise exception '% no implemented for follow', reference::text;
+    end if;
 end;
 $$;