Improve docker install examples

Removes the PGRST_DB_SCHEMA variable which is public by default now.

Removes the PGRST_DB_ANON_ROLE variable, because using the authenticator role or even a superuser is very bad practice.

Replaces the postgres superuser with app_user, because using a superuser to connect to postgres is very bad practice.

Signed-off-by: Wolfgang Walther <walther@technowledgy.de>

docs/install.rst

@@ -130,9 +130,7 @@ The first way to run PostgREST in Docker is to connect it to an existing native
 
   # Run the server
   docker run --rm --net=host -p 3000:3000 \
-    -e PGRST_DB_URI="postgres://postgres@localhost/postgres" \
-    -e PGRST_DB_SCHEMA="public" \
-    -e PGRST_DB_ANON_ROLE="postgres" \
+    -e PGRST_DB_URI="postgres://app_user:password@localhost/postgres" \
     postgrest/postgrest
 
 The database connection string above is just an example. Adjust the role and password as necessary. You may need to edit PostgreSQL's :code:`pg_hba.conf` to grant the user local login access.
@@ -176,8 +174,6 @@ To avoid having to install the database at all, you can run both it and the serv
         - "3000:3000"
       environment:
         PGRST_DB_URI: postgres://app_user:password@db:5432/app_db
-        PGRST_DB_SCHEMA: public
-        PGRST_DB_ANON_ROLE: app_user #In production this role should not be the same as the one used for the connection
         PGRST_OPENAPI_SERVER_PROXY_URI: http://127.0.0.1:3000
       depends_on:
         - db