This is a breaking change that will require you to change your Phoebe
settings for PostgreSQL.
* New database configuration options
* Accounts no longer automatically create databases
* Databases have `owners' that tie them back to an account
* Databases have `users' that grant accounts full access
* Databases have `readers' that grant read-only access to accounts
* Accounts can use `ident' authentication for local connections if
you enable the `allowIdent' option.
* Existing accounts that are not configured via Phoebe will be
locked so they cannot be used. That way if you delete a user from
Phoebe the account will continue to exist, but won't have access
to anything.
* Services that need password files will automatically depend on the
appropriate NixOps key service as necessary.
* New `sourcedFile` option for Rails applications to load a Bash
script just before starting the Rails service. Useful for setting
secret environment variables.
