Added info about SERVER_URL to docs (#4433)

* Added info about reverse-proxy and SERVER_URL to docs

* Fixed comments

* Fix lint

---------

Co-authored-by: Maciej Siwek <maciej.siwek@resly.se>
Co-authored-by: Lucas Bordeau <bordeau.lucas@gmail.com>

packages/twenty-docs/docs/start/self-hosting/docker-compose.mdx

@@ -6,14 +6,33 @@ sidebar_custom_props:
 ---
 # Step by step instructions:
 
-1) Copy the [.env.example](https://github.com/twentyhq/twenty/blob/main/packages/twenty-server/.env.example) into a `.env` in the same directory where your `docker-compose.yml` file will be
+1. Copy the [.env.example](https://github.com/twentyhq/twenty/blob/main/packages/twenty-server/.env.example) into a `.env` in the same directory where your `docker-compose.yml` file will be
-2) Run the command `openssl rand -base64 32` three times, make note of the string for each
+2. Run the command `openssl rand -base64 32` three times, make note of the string for each
-3) Replace the three "replace_me_with_a_random_string_access" with the three random strings you just generated.
+3. In your .env file, replace the three "replace_me_with_a_random_string_access" with the three random strings you just generated.
-4) Create a `docker-compose.yml` file from the example below.
+
-5) Run the command `docker-compose up -d`
+```
-6) Go to http://localhost:3001 and see your docker instance.
+ACCESS_TOKEN_SECRET=replace_me_with_a_random_string_access 
+LOGIN_TOKEN_SECRET=replace_me_with_a_random_string_login 
+REFRESH_TOKEN_SECRET=replace_me_with_a_random_string_refresh
+```
+
+4. Create a `docker-compose.yml` file from the example below.
+5. Run the command `docker-compose up -d`
+6. Go to http://localhost:3001 and see your docker instance.
+
+## Troubleshooting 
+
+### Not able to login 
+
+If you encounter errors, (not able to log into the application after inputting an email) after the inital setup, try running `docker exec -it twenty_backend_1 yarn database:reset` and see if that solves your issue. 
+
+### Cannot connect to server, running behind a reverse proxy
+
+Complete step three and four with : 
+
+3. Add `SERVER_URL=https://<your-api-url.com>` to your `.env`
+4. Uncomment `SERVER_URL=${SERVER_URL}` in your `docker-compose.yml`
 
-- If you encounter errors, (not able to log into the application after inputting an email) after the inital setup, try running `docker exec -it twenty_backend_1 yarn database:reset` and see if that solves your issue. 
 ## Production docker containers
 
 Prebuilt images for both Postgres, frontend, and back-end can be found on [docker hub](https://hub.docker.com/r/twentycrm/).
@@ -59,6 +78,8 @@ services:
       - ACCESS_TOKEN_SECRET=${ACCESS_TOKEN_SECRET}
       - LOGIN_TOKEN_SECRET=${LOGIN_TOKEN_SECRET}
       - REFRESH_TOKEN_SECRET=${REFRESH_TOKEN_SECRET}
+      # Uncomment if behind a reverse proxy
+      # - SERVER_URL=${SERVER_URL}
     depends_on:
       - db