docs: add assignment 4

Assignment4.md

@@ -0,0 +1,60 @@
+# Assignment-4
+
+## To set up and execute
+
+1. Download and unzip the file for [Assignment 4](https://github.com/CS3219-AY2324S1/ay2324s1-course-assessment-g17/archive/refs/tags/Assignment-4.zip). `cd` into it.
+2. Set up environment variables.
+   > The unredacted environment variable `MONGO_CONNECTION_STRING` can be found in our Canvas submission for private variables.
+
+- frontend
+  - Save the frontend variables under `frontend/.env`.
+    ```
+    REACT_APP_BACKEND_URL=http://localhost:8080/api
+    REACT_APP_USER_SERVICE_BACKEND_URL=http://localhost:8000/
+    ```
+- user-service
+
+  - Save the user-service variables twice in `backend/user-service/.env` and `backend/user-service/.env.docker`
+    - backend/user-service/.env.docker
+    ```
+    DATABASE_URL="postgresql://postgres:postgres@postgres:5432/peerprep?schema=public"
+    PORT=8000
+    JWT_SECRET="secret"
+    FRONTEND_URL="http://localhost:3000"
+    ```
+    - backend/user-service/.env
+      (need to change DATABASE_URL because we would not be in docker compose's network)
+    ```
+    DATABASE_URL="postgresql://postgres:postgres@localhost:5432/peerprep?schema=public"
+    PORT=8000
+    JWT_SECRET="secret"
+    FRONTEND_URL="http://localhost:3000"
+    ```
+
+- question-service
+  - Save the question-service variables under `backend/question-service/.env`
+    ```
+    MONGO_CONNECTION_STRING=<redacted>
+    PORT=8080
+    FRONTEND_URL="http://localhost:3000"
+    ```
+
+3. Actually run it with Docker.
+
+- Option 1 (recommended): Docker Compose
+  1. cd into all frontend/backend services and type `npm install`
+  2. `docker-compose up`
+- Option 2: Running individually with `docker`
+  1. Navigate to the folder of the zip file you unzipped previously.
+  2. `cd backend/question-service`
+  3. `docker build . -t question-service && docker run -p 8080:8080 -d question-service`
+  4. Open another terminal tab. Repeat step 1.
+  5. `cd backend/user-service`
+  6. `docker build . -t user-service && docker run -p 8000:8000 -d user-service`
+
+4. Testing
+
+- If you used option 1, the frontend should be up as well, navigate to http://localhost:3000 to see the results.
+- If you used option 2, you can use some curl commands to verify the services work
+  - Question service: `curl localhost:8080/api/questions/1`
+  - User service: `curl localhost:8000/currentUser`