feat: sync rich text message support

deploy/migrations/0050_rich_message_content_checks.down.sql

@@ -0,0 +1,20 @@
+ALTER TABLE public.channel_messages
+    DROP CONSTRAINT IF EXISTS channel_messages_content_check;
+
+ALTER TABLE public.channel_messages
+    ADD CONSTRAINT channel_messages_content_check
+    CHECK (
+        body <> ''::text
+        OR action <> '{}'::jsonb
+        OR media <> '{}'::jsonb
+    );
+
+ALTER TABLE public.private_messages
+    DROP CONSTRAINT IF EXISTS private_messages_nonempty_body;
+
+ALTER TABLE public.private_messages
+    ADD CONSTRAINT private_messages_nonempty_body
+    CHECK (
+        body <> ''::text
+        OR media <> '{}'::jsonb
+    );