chore: Upgrade to pg_graphql v0.2.0

[dthyresson]

See: supabase/pg_graphql#146

Features to consider/test:

• New error key handling
• Docs around the rebuild_schema() function

May need @olirice help to update the existing project as well.

[olirice]

the only compatibility thing to be aware of with this change is that errors have moved in one level to conform to the graphql spec

Before

{
    "errors": "something went wrong"
}

After

{
    "errors": {
        "message": "something went wrong"
    }
}

[dthyresson]

Also, will want to migrate project to a new Supabase project because:

(currently) have a filter for upgrades so that they only apply to projects created after the GA date

Until then, the currently deployed project will not receive pg_graphql updates.

See the following migration guide: https://supabase.com/docs/guides/database#migrating-between-projects