Prepare for Netbox 4.0

docker-entrypoint.sh: clarify default token message ...

When a default admin API token is found, a warning is displayed. As it is only called "token", some users might not know what token is referred to. Also the message should give a hint or link to a documentation on how to remove it.

Catch DoesNotExist preventing startup ...

Fixes failing startup because of python error:

```
Traceback (most recent call last):
  File "/opt/netbox/netbox/./manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/opt/netbox/venv/lib/python3.10/site-packages/django/core/management/__init__.py", line 446, in execute_from_command_line
    utility.execute()
  File "/opt/netbox/venv/lib/python3.10/site-packages/django/core/management/__init__.py", line 440, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/opt/netbox/venv/lib/python3.10/site-packages/django/core/management/base.py", line 402, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/opt/netbox/venv/lib/python3.10/site-packages/django/core/management/base.py", line 448, in execute
    output = self.handle(*args, **options)
  File "/opt/netbox/venv/lib/python3.10/site-packages/django/core/management/commands/shell.py", line 127, in handle
    exec(sys.stdin.read(), globals())
  File "<string>", line 2, in <module>
  File "/opt/netbox/venv/lib/python3.10/site-packages/django/db/models/manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/opt/netbox/venv/lib/python3.10/site-packages/django/db/models/query.py", line 650, in get
    raise self.model.DoesNotExist(
users.models.Token.DoesNotExist: Token matching query does not exist.
```

Don't create superuser with default credentials

Fixes #947: Rebuild search index when needed ...

This rebuilds the search index when models where updated.

Removed warning for initializer scripts

Initializers are now a plugin

Print last line of django db connection error while waiting for db to start ...

Fixes #562

django-cacheops has been removed from Netbox 3.0.0

Optimise migrations on startup ...

The migrations are only started if there are some that have not been
applied. Additionally the maintenace task needed after an update are
now run after the migrations

Fix quoting of exec argument in the entrypoint script

Format shell scripts with shfmt

Fix shellcheck complaint

NetBox should always be referred to as NetBox ...

Fix all instances of "Netbox".

```Shell
git ls-files -z . | xargs --null -I '{}' find './{}' -type f -print0 | xargs --null sed --in-place --regexp-extended 's#Netbox#NetBox#g;'
```

Ref: https://netbox.readthedocs.io/en/stable/development/style-guide/#branding

Gunicorn is replaced with nginx-unit ...

We now serve Netbox with an nginx-unit instance instead of Gunicorn.
This allows us to get rid of the extra Nginx container because Unit is
also serving the static files. The static files are now collected at container
buildtime instead of every startup.

Prefer secret to env variable if both are configured

Building the Docker image with Github Actions

Merge pull request #186 from netbox-community/non-root ...

Non root

Massive speedup in executing startup_scripts

set umask in entrypoint

fix typo

Introduce $SKIP_SUPERUSER ...

This adds a new variable to skip the creation of the superuser.
That is useful for LDAP and for production environments.

Fixes #160

Make startup scripts optional ...

To optimize the application boot time the startup scripts can now be
disabled by an ENV variable. The default when the variable is not set,
is to run the startup scripts. This means that the default behaviour is
not changed from earlier releases.

Remove deprecation warning for netboxcommunity images

Consistent variable use in build scripts

Update docker-entrypoint.sh ...

Make netbox-docker function with  v2.4-beta1 again, fixes #84.

> The shell --plain option is deprecated in favor of -i python or --interface python.
> The shell --interface option now accepts python to force use of the “plain” Python interpreter.
https://docs.djangoproject.com/en/2.0/releases/1.10/#deprecated-features-1-10

Fixed missing "

Added username and email of superuser

Do not print the admin credentials. All outputs from STDOUT may end up in a central log store. This will compromise the superuser credentials.

✨ Include Initializers ...

Initializers are startup scripts for common tasks like creating custom
fields. These are problems many users of Netbox Docker potentially face
and are therefore worth sharing.