Fix for issue #223

[strawhat-x]

Fix Date & DateTime custom fields types for Image object with DjangoJSONEncoder.

[strawhat-x]

Once the plugin is installed in your netbox with this version run commands below:
python3 netbox/manage.py test netbox_docker_plugin.tests.image.test_force_pull_image_with_special_cf.ForcePullImageWithSpecialCFTestCase.test_force_pull_with_date_custom_field --keepdb -v 2

AND

python3 netbox/manage.py test netbox_docker_plugin.tests.image.test_force_pull_image_with_special_cf.ForcePullImageWithSpecialCFTestCase.test_force_pull_with_datetime_custom_field --keepdb -v 2

[FredSequeira]

Newly added tests are currently failing. Please fix the issue
Testing on:
Netbox version: v4.3.7
Plugin version: 4.11.0

Thank you.

[strawhat-x]

FredSequeira

What version of Netbox do you need please? v3.7.8 or v4.3.7?

[FredSequeira]

Hello,
to open the issue we used NB version 3.7.8 but if we want to target a version for the fix I think we can say Netbox version >= 4.0.11, for me that is fine.
My previous comment was made by testing with version 4.3.7 because this fix, from what I understand, was only done on top of a plugin version that has the requirement of Min Netbox Version = 4.3.7, that would mean that even if I wanted I could not test the fix on a netbox version 3.7.8.

Thank you

[fanshan]

@strawhat-x Can you rebase your PR?