See [Linear issue
2-1627](https://linear.app/unleash/issue/2-1627/db-permissions-update-docs-and-migration-guides).
Since we now use functions, we need more permissions than just GRANT ALL
PERMISSIONS ON DATBASE. In addition we need to be allowed to create
functions in the schema that's actually being used. This PR takes the
easy way out and say that we need OWNER privileges on the database. That
guarantees that we can do all we do in our migration scripts.
### Discussion points
We might encounter some pushback on this, if so, we'll need to say that
we need
`GRANT ALL PRIVILEGES ON ALL FUNCTIONS IN <schema>` in addition to GRANT
ALL PRIVILEGES ON DATABASE, where <schema> is the schema selected in
their configuration.
