Add explicit PostgreSQL note about scram-sha-256

postgres/content.md

@@ -93,6 +93,8 @@ See the PostgreSQL documentation on [`pg_hba.conf`](https://www.postgresql.org/d
 
 **Note 2:** If you set `POSTGRES_HOST_AUTH_METHOD` to `trust`, then `POSTGRES_PASSWORD` is not required.
 
+**Note 3:** If you set this to an alternative value (such as `scram-sha-256`), you might need additional `POSTGRES_INITDB_ARGS` for the database to initialize correctly (such as `POSTGRES_INITDB_ARGS=--auth-host=scram-sha-256`).
+
 ### `PGDATA`
 
 This optional variable can be used to define another location - like a subdirectory - for the database files. The default is `/var/lib/postgresql/data`. If the data volume you're using is a filesystem mountpoint (like with GCE persistent disks) or remote folder that cannot be chowned to the `postgres` user (like some NFS mounts), Postgres `initdb` recommends a subdirectory be created to contain the data.