Add OIDCClient for django tests

[kerrermanisNL]

Add an OIDCClient for django tests. This can be useful when you need to use the oidc_id_token in your views. The default Django test client does not provide this. By making use of this new client your requests will contain a oidc_id_token key with a random value (which you can specify). Because there is no easy way to do this yourself for the Django test client (you can either fix it by writing a custom client or by using a RequestFactory, both are not very ideal) I thought it would be useful to provide a default client that comes with the mozilla library.

[kerrermanisNL]

Note that I tested it like this because the session property of the django test client is a little weird to wrap your head around. So instead of instantiating and specifying a new oidc token and refreshing the session, I thought a test like this would be better.

[codecov-io]

Codecov Report

Merging #318 into master will increase coverage by 0.2%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #318     +/-   ##
=========================================
+ Coverage   88.36%   88.57%   +0.2%     
=========================================
  Files           7        8      +1     
  Lines         447      455      +8     
=========================================
+ Hits          395      403      +8     
  Misses         52       52

Impacted Files	Coverage Δ
mozilla_django_oidc/test.py	100% <100%> (ø)

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[kerrermanisNL]

Usage when specifying this class remains the same for the test client, you just have to specify it in the test case:

class TestSomething(TestCase):
    client_class = OIDCClient

    def test_calls_something_with_oidc_token(self):
        # Functionality remains exactly the same, except the view does not die when 
        # accessing `request.session['oidc_id_token']`
        self.client.get('/someting/')

[kerrermanisNL]

Hi there, could someone have a look at this?

[kerrermanisNL]

Could someone have a look at this?

[kerrermanisNL]

Bump :)

[hartwork]

I think deriving from TestCase may work better since none of the things added by SimpleTestCase seem needed here — are they?

[kerrermanisNL]

I've changed it to make use of unittest.Testcase. I assume that's what you mean, since the Django TestCase class inherits from SimpleTestCase :)

[hartwork]

It's the other way around — see https://github.com/django/django/blob/a6b3938afc0204093b5356ade2be30b461a698c5/django/test/testcases.py#L146 — but thanks for the change!

[kerrermanisNL]

Yes that's what I meant :) django.TestCase inherits from django.SimpleTestCase which inherits from unittest.TestCase 😄 Anyhoo, no worries, thanks for the feedback :)

[gene1wood]

@kerrermanisNL I've removed the set of reviewers you requested review from as that group are the org owners. They don't have context on this mozilla-django-oidc repo and don't perform PR reviews in it. I'd recommend reaching out to contributors if you're looking for review.