Fix coding standards

nicolasgraph → closed merge request !8

nicolasgraph → changed the visibility of the branch 3519229-fix-coding-standards to hidden.

I just rerolled the MR into a new branch.
It still requires attention for this last phpstan error:

 ------ -------------------------------------------------------------------------- 
  Line   tests/modules/commerce_payplug_tests/src/Services/PayPlugTestService.php  
 ------ -------------------------------------------------------------------------- 
  94     \Drupal calls should be avoided in classes, use dependency                
         injection instead                                                         
 ------ -------------------------------------------------------------------------- 

The current MR still requires attention for this last phpstan error:

 ------ -------------------------------------------------------------------------- 
  Line   tests/modules/commerce_payplug_tests/src/Services/PayPlugTestService.php  
 ------ -------------------------------------------------------------------------- 
  94     \Drupal calls should be avoided in classes, use dependency                
         injection instead                                                         
 ------ -------------------------------------------------------------------------- 

Let's merge this to go forward.
Opening a dedicated issue for the last tricky phpstan error.