Anonymize docker compose

[rca]

Greetings,

This pull request makes a couple of changes to docker-compose to make it safer to use. The values for all environment variables have been removed from docker-compose.yml and they should, instead, be set in one of two ways:

• export them as environment variables in the shell that docker-compose is being run from
• write the values to a .env file alongside docker-compose.yml, which is automatically read by docker-compose and looks like this:

[berto@g6]$ cat .env
POSTGRES_DB=localshop
POSTGRES_USER=localshop
POSTGRES_PASSWORD=shopping
DJANGO_SECRET_KEY=a7d03faa0c054b3dba38b396bf3c7996
DATABASE_URL=postgresql://localshop:shopping@db/localshop
DJANGO_MEDIA_ROOT=/opt/localshop/media

This change makes the docker-compose file generic and allows the end-user to inject their own values without having to change the file.

Additionally, I updated postgres to the official image and verified that it works without any issue. Note: the database name, username, and password environment variables have changed accordingly.

[codecov]

Codecov Report

Merging #188 into develop will increase coverage by 3.12%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #188      +/-   ##
===========================================
+ Coverage    82.15%   85.28%   +3.12%     
===========================================
  Files           36       33       -3     
  Lines         1390     1155     -235     
===========================================
- Hits          1142      985     -157     
+ Misses         248      170      -78

Impacted Files	Coverage Δ
localshop/apps/dashboard/views.py	57.14% <0%> (-4.1%)	⬇️
localshop/apps/dashboard/urls.py	100% <0%> (ø)	⬆️
localshop/__init__.py
localshop/utils.py
localshop/views.py
localshop/urls.py
localshop/apps/permissions/migrations/__init__.py	100% <0%> (ø)
localshop/apps/permissions/utils.py	92.5% <0%> (+9.16%)	⬆️

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[rca]

Checking in on this, ping @mvantellingen