feature #7: add function "find_comments_by_parent"

src/main/resources/sql/functions/comment/find_comments_by_parent.sql

@@ -0,0 +1,26 @@
+create or replace function find_comments_by_parent(
+    _parent_id uuid,
+    "limit" int default 50,
+    "offset" int default 0,
+    out resource json,
+    out total int
+) language plpgsql as
+$$
+begin
+    select json_agg(t), (select count(id) from "comment" com where com.parents_ids @> array[_parent_id])
+    into resource, total
+    from (
+        select
+            com.*,
+            json_build_object('id', com.target_id) as target,
+            find_citizen_by_id(com.citizen_id) as citizen
+        from "comment" as com
+        where com.parents_ids @> array[_parent_id]
+        order by com.parents_ids nulls first, created_at desc,
+        com.created_at desc
+        limit "limit" offset "offset"
+    ) as t;
+end;
+$$;
+
+-- drop function if exists find_comments_by_parent(uuid, int, int);