Python 3.7 support

[immomp]

Hi,

the documentation states that you support Python 3.7 but it appears that you use the walrus operator, for example here:

django-utm-tracker/utm_tracker/request.py

Line 44 in 68b3794

if akey := request.GET.get(ad_key):

This breaks 3.7 support, I think.

Thank you!
(also for a great app)

[hugorodgerbrown]

Hi @immomp - that's correct, thanks for pointing this out. I will update the docs and the classifiers, and tag the last commit that supports Python 3.7, but I won't update the main branch to remove the := as we an deliberate "forward-only and deprecate" policy - as new syntax comes in we adopt early.