Insecure Default Configuration

Hi there,

if one runs the [default migration](https://github.com/AppFlowy-IO/AppFlowy-Supabase/tree/main/postgres) security warnings pop up in supabase. These security warnings are related to [Row-Level-Security](https://supabase.com/docs/guides/database/database-advisors?queryGroups=lint&lint=0013_rls_disabled_in_public) and the [Security Definer View](https://supabase.com/docs/guides/database/database-advisors?queryGroups=lint&lint=0010_security_definer_view).

As a developer, I would like to have a migration which avoids these errors in the first place, so it is easier to have a safe supabase environment without the manual effort which is necessary now.

I am not 100% sure, but I think some steps to achieve this would be:

RLS
1. Enable RLS on all tables
2. Determine which tables need anonymous access (and which level of access specifically)
3. Create policies for those

Security Definer View
(I am not sure about this yet)