feat(api) add refresh.rs

backend/post.sql

@@ -5,3 +5,10 @@ CREATE TABLE IF NOT EXISTS Post
     content     TEXT         NOT NULL,
     last_update TIMESTAMP
 );
+
+INSERT INTO Post (post_id, title, content, last_update)
+VALUES (?1, ?2, ?3, ?4)
+ON CONFLICT (post_id)
+    DO UPDATE SET title       = excluded.title,
+                  content     = excluded.content,
+                  last_update = excluded.last_update