feat(documentation): how to initilize data from a backup

documentation/GettingStarted/init_data.md

-Loading initial/example data into the app
-=====
+# Initializing data in the app
+
+You have to options to initialize data in the app:
+
+- From a production database backup,
+- From dummy data.
+
+## From a production database backup
+
+If you have access to [a production database backup](Application/deploy?id=creating-a-database-dump), follow these instructions:
+
+- Download the dump, and move it to the location: `/tmp/rex-dri.dump.gpg`
+- decrypt it (**You will need a passphrase for this.**):
+
+```bash
+cd /tmp && gpg-zip --decrypt rex-dri.dump.gpg
+test -f /tmp/rex-dri.dump && echo "Database dump decrypted"
+```
+
+- Restore the backup (run the following inside the rex-dri root folder on your computer)
+
+```bash
+# Down everything and re-up only the database
+docker-compose down
+docker-compose up database
+```
+
+```bash
+# wait for the database to be up and in another shell
+# Delete the existing database and restore the database
+docker-compose exec database dropdb -U postgres postgres
+docker-compose exec database createdb -U postgres postgres
+docker-compose exec database rm -rf /tmp/rex-dri.dump
+docker cp /tmp/rex-dri.dump rex-dri_database_1:/tmp/rex-dri.dump
+
+docker-compose exec database pg_restore -U postgres -d postgres /tmp/rex-dri.dump
+
+# Down everything
+docker-compose down
+```
+
+- If you (identified by your CAS account) are not a admin user on the website, do the following:
+
+```bash
+# Restart and set superuser
+make dev
+make shell_backend
+# replace 'chehabfl' by your own UTC login
+echo "from base_app.models import User; user = User.objects.get(username='chehabfl'); user.is_superuser = True; user.is_staff = True; user.save();" | ./manage.py shell
+```
+
+_N.B. If the last part fails, it's because you have never connected REX-DRI before the dump :crying:. Open [http://localhost:8000/app/](http://localhost:8000/app/), connect with the CAS, and retry the last command._
+
+## With dummy data
 
 To load some basic data in the app, you can use the python classes: `loadCountries`, `loadUniversities`, etc. available in `backend/backend_app/load_data/loading_scripts`.
 
@@ -22,7 +74,6 @@ from backend_app.load_data.load_all import load_all
 load_all()
 ```
 
-*NB: Those scripts are tested so they should work.*
-
+_NB: Those scripts are tested so they should work._
 
 By doing so, an admin user is created according to the environment variables `DJANGO_ADMIN_USERNAME` and `DJANGO_ADMIN_PASSWORD` that are set (in our case) in the `docker-compose` file.