Adds test case for LoginView

[iamdipanshusingh]

Hey, I just made a Pull Request!

Description

Adds test case for LoginView

Motivation and Context

Have you tested this? If so, how?

Checklist for PR author(s)

• Changes are covered by unit tests (no major decrease in code coverage %).
• All tests pass.
• Docstring coverage is 100% via interrogate drf_user (I mean, we should set a good example 😄).
• Updates to documentation:
  • Document any relevant additions/changes in README.md.
  • Manually update both the README.md and docs/index.rst for any new changes.
  • Any changed/added classes/methods/functions have appropriate versionadded, versionchanged, or deprecated directives. Find the appropriate next version in the project's __init__.py file.

Release note

[codecov]

Codecov Report

Merging #22 into master will increase coverage by 18.73%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master      #22       +/-   ##
===========================================
+ Coverage   26.03%   44.77%   +18.73%     
===========================================
  Files          17       17               
  Lines         603      603               
===========================================
+ Hits          157      270      +113     
+ Misses        446      333      -113     

Flag	Coverage Δ
#unittests	44.77% <ø> (+18.73%)	⬆️

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

Impacted Files	Coverage Δ
drf_user/serializers.py	38.54% <0.00%> (+38.54%)	⬆️
drf_user/views.py	47.20% <0.00%> (+47.20%)	⬆️

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[sumit4613]

LGTM 💯