Added enforce_encoding

[WisdomPill]

Fixes: #595

Added enforce_encoding option for encoding even bool and int using serializer when this behavior is wanted.

@syphar for some strange reason I can't add you in the reviewers and it did not even suggest you when I was tagging you

[codecov]

Codecov Report

Merging #602 (7c3bdc1) into master (4e7f2d4) will decrease coverage by 23.8%.
The diff coverage is 40.0%.

@@            Coverage Diff            @@
##           master    #602      +/-   ##
=========================================
- Coverage    57.8%   34.0%   -23.7%     
=========================================
  Files          39      39              
  Lines        2497    2477      -20     
  Branches       73      71       -2     
=========================================
- Hits         1441     840     -601     
- Misses       1041    1566     +525     
- Partials       15      71      +56     

Flag	Coverage Δ
mypy	34.0% <40.0%> (+0.1%)	⬆️
tests	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
django_redis/client/default.py	39.0% <33.4%> (-51.4%)	⬇️
tests/test_backend.py	15.2% <44.5%> (+0.5%)	⬆️
django_redis/client/sharded.py	5.9% <0.0%> (-80.1%)	⬇️
django_redis/pool.py	11.0% <0.0%> (-66.0%)	⬇️
django_redis/cache.py	34.2% <0.0%> (-62.8%)	⬇️
django_redis/serializers/msgpack.py	37.5% <0.0%> (-62.5%)	⬇️
django_redis/client/sentinel.py	22.8% <0.0%> (-54.5%)	⬇️
django_redis/serializers/base.py	50.0% <0.0%> (-50.0%)	⬇️
django_redis/serializers/pickle.py	54.6% <0.0%> (-45.4%)	⬇️
... and 9 more

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[syphar]

This is more a design question, so not to me to decide, but:

In my mind this is not the solution but only a workaround. Users of the library have to know that they need to use enforce_encoding when they want to cache specific data-types.

Since we're already special-casing bool, because isinstance(bool, int) is True,
why not just adding a special case enum.Enum too?

@syphar for some strange reason I can't add you in the reviewers and it did not even suggest you when I was tagging you

Only users part of the repo can be added as reviewers, and are in the suggestion.

[WisdomPill]

I like your idea, I would happily change it. I want to point out what I think is the reason why there are this exceptions. I think it is because of space, numbers and booleans use much more space than pickle serialized objects.