Restart celery after any changes to the code

[StuartMacKay]

Ensure that any celery workers are restarted so that they pick up and changes to the code after a deploy.

This pull request is dependent on the changes in YPCrumble/django-default-project#2 which add celery to the django default project so the molecule tests pass.

[YPCrumble]

@StuartMacKay about to merge this in, thank you!!! It looks like there's one place missing, which is to restart Celery when the celery configuration file changes, or these two sections:

- name: Create the script file for {{ celery_application_name }}
  ansible.builtin.template: src={{ celery_template_file }}
            dest={{ celery_scripts_dir }}/{{ celery_application_name }}_start
            owner={{ celery_user }}
            group={{ celery_group }}
            mode=0755

- name: Create the script file for {{ celery_beat_application_name }}
  ansible.builtin.template: src={{ celery_beat_template_file }}
            dest={{ celery_scripts_dir }}/{{ celery_beat_application_name }}_start
            owner={{ celery_user }}
            group={{ celery_group }}
            mode=0755

Happy for you to make those additions or if not I'll make a separate PR soon and close this one. Thank you again, hoping you're still using this repo!