CREATE DOMAIN not added to migration

[ChristianSi]

Bug report

• [x] I confirm this is a bug with Supabase, not with my own application.
• [x] I confirm I have searched the Docs, GitHub Discussions, and Discord.

Describe the bug

As Media Type Handlers documents, a CREATE DOMAIN command is needed to return custom media types. However, supabase db diff does not add these commands to the generated migration, so pushing the migration to other systems will fail.

To Reproduce

Create a custom domain and a function returning it, for example:

create domain "text/plain" as text;

CREATE OR REPLACE FUNCTION echo_service(input text)
 RETURNS "text/plain"
 LANGUAGE plpgsql
AS $function$declare
begin
  -- Echo input back as plain text
  perform set_config('response.headers', '[{"Content-Type": "text/plain"}]', true);
  return input;
end;$function$
;

Create a migration calling supabase db diff --local.

Expected behavior

Both the create domain and the CREATE OR REPLACE FUNCTION commands are added to the migration.

Actual behavior

Only the CREATE OR REPLACE FUNCTION command is added to the migration.

As a result, ERROR: 42704: type "text/plain" does not exist will be thrown if trying to apply the migration elsewhere.

System information

All/latest.