server: enusre post.link is not null and not empty

server/migrations/20241225180250_post-link-non-empty.down.sql

@@ -0,0 +1,7 @@
+ALTER TABLE
+    post
+ALTER COLUMN
+    link DROP NOT NULL;
+
+ALTER TABLE
+    post DROP CONSTRAINT link;

server/migrations/20241225180250_post-link-non-empty.up.sql

@@ -0,0 +1,17 @@
+DELETE FROM
+    post
+WHERE
+    link IS NULL
+    OR link = '';
+
+ALTER TABLE
+    post
+ALTER COLUMN
+    link
+SET
+    NOT NULL;
+
+ALTER TABLE
+    post
+ADD
+    CONSTRAINT link CHECK (link <> '');