[1.7.x] Fixed #22372 -- Improved description of WizardView.get_context_data().

Thanks simon29 for the report.

Backport of a8e2ec0e82 from master
[1.7.x] Fixed #22363 -- Correctly serialize `django.utils.datetime_safe` objects.

Thanks to linovia for the report.

Backport of 074d3183d9 from master
[1.7.x] Refactored and commented strip_tags utility

Backport of c28beb4291 from master.