fix:small docs fix

Author: moizpgedge

docs/Supported-services/Postgrest-docs.md

@@ -4,7 +4,7 @@ PostgREST serves a REST API directly from your Postgres schema. The Control Plan
 
 ## Before You Deploy
 
-Grant the platform roles access to the schemas you want to expose. The Control Plane creates the service user. You only need to grant schema permissions.
+No new roles or schemas need to be created. `public`, `pgedge_application_read_only`, and `pgedge_application` already exist. You only need to grant them access to your schema.
 
 ```sql
 -- Anonymous read access
@@ -69,16 +69,21 @@ curl http://host-1:3100/products
 
 ### Authenticated write
 
-Sign this payload with your `jwt_secret` using HS256:
+Generate a JWT signed with your `jwt_secret`:
 
-```json
-{ "role": "pgedge_application", "exp": 9999999999 }
+```sh
+python3 - <<'EOF'
+import jwt
+SECRET = "a-secret-key-of-at-least-32-characters"
+token = jwt.encode({"role": "pgedge_application"}, SECRET, algorithm="HS256")
+print(token)
+EOF
 ```
 
 ```sh
 curl -X POST http://host-1:3100/products \
     -H "Content-Type: application/json" \
-    -H "Authorization: Bearer <your-jwt>" \
+    -H "Authorization: Bearer <token-from-above>" \
     --data '{"name": "Widget", "price": 9.99}'
 ```