feat(backend): refactor/cleaned/ infer get_serializer

* Cleaned all init files
* Infer the serializer from the model instead of having it in the models
* Updated the doc accordingly
* Fixed typos

Fixes #93
Fixes #85
Status Job ID Name Coverage
  Check
passed #481936
docker
check_back

00:00:22

passed #481937
docker
check_front

00:01:18

 
  Test
passed #481938
docker
test_back

00:00:45

88.0%
passed #481939
docker
test_frontend

00:01:15

 
  Lint
passed #481941
docker
eslint

00:01:18

passed #481940
docker
flake8

00:00:12

 
  Svg Gen Docu
passed #481942
docker
generate_UML_svg

00:00:15

 
  Documentation
passed #481943
docker
pages

00:00:12

 
  Deploy
passed pages:deploy

00:00:00