Update databases/postgres/README.md (actix#554)

* Update databases/postgres/README.md

Add sudo -u postgres to relevant commands

Add privilege granting step for new user

Add -i flag to curl command to show HTTP response code

* Update databases/postgres/README.md

Add more options for accomplishing tasks

Add note regarding

Author: Raymi306

databases/postgres/README.md

@@ -9,6 +9,11 @@
 
 ## Instructions
 
+### NOTE:
+
+You may need to ensure that you are running the commands with the correct SQL user.
+On many Linux distributions you may prefix the shell commands with `sudo -u postgres`
+
 1. Create database user
 
    ```shell
@@ -19,12 +24,22 @@
 
    This step is **optional** and you can also use an existing database user for that. Just make sure to replace `test_user` by the database user of your choice in the following steps and change the `.env` file containing the configuration accordingly.
 
+   An alternative using SQL:
+   ```sql
+   CREATE USER test_user WITH PASSWORD 'testing';
+   ```
+
 2. Create database
 
    ```shell
    createdb -O test_user testing_db
    ```
 
+   An alternative using SQL:
+   ```sql
+   CREATE DATABASE testing_db OWNER test_user;
+   ```
+
 3. Initialize database
 
    ```shell
@@ -33,7 +48,15 @@
 
    This step can be repeated and clears the database as it drops and recreates the schema `testing` which is used within the database.
 
-4. Create `.env` file:
+4. Grant privileges to new user
+
+   ```sql
+   GRANT ALL PRIVILEGES ON SCHEMA testing TO test_user;
+   GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA testing TO test_user;
+   GRANT ALL PRIVILEGES ON ALL SEQUENCES IN SCHEMA testing TO test_user;
+   ``` 
+
+5. Create `.env` file:
 
    ```ini
    SERVER_ADDR=127.0.0.1:8080
@@ -45,13 +68,13 @@
    PG.POOL.MAX_SIZE=16
    ```
 
-5. Run the server:
+6. Run the server:
 
    ```shell
    cargo run
    ```
 
-6. Using a different terminal send an HTTP POST request to the running server:
+7. Using a different terminal send an HTTP POST request to the running server:
 
    ```shell
    echo '{"email": "ferris@thecrab.com", "first_name": "ferris", "last_name": "crab", "username": "ferreal"}' | http -f --json --print h POST http://127.0.0.1:8080/users
@@ -60,7 +83,7 @@
    **...or using curl...**
 
    ```shell
-   curl -d '{"email": "ferris@thecrab.com", "first_name": "ferris", "last_name": "crab", "username": "ferreal"}' -H 'Content-Type: application/json' http://127.0.0.1:8080/users
+   curl -i -d '{"email": "ferris@thecrab.com", "first_name": "ferris", "last_name": "crab", "username": "ferreal"}' -H 'Content-Type: application/json' http://127.0.0.1:8080/users
    ```
 
    A unique constraint exists for username, so sending this request twice will return an internal server error (HTTP 500).