backends: Move Facebook Limited Login to separate module

[nijel]

Proposed changes

This removes jose dependency from Facebook backend.

Fixes #773

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[codecov]

Codecov Report

Merging #778 (59eb5e9) into master (d1d91ae) will increase coverage by 0.00%.
The diff coverage is 64.00%.

❗ Current head 59eb5e9 differs from pull request most recent head 10cc300. Consider uploading reports for the commit 10cc300 to get more accurate results

@@           Coverage Diff           @@
##           master     #778   +/-   ##
=======================================
  Coverage   77.34%   77.34%           
=======================================
  Files         325      326    +1     
  Lines        9864     9865    +1     
  Branches     1174     1174           
=======================================
+ Hits         7629     7630    +1     
  Misses       2084     2084           
  Partials      151      151           

Flag	Coverage Δ
unittests	77.34% <64.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
social_core/backends/facebook.py	54.13% <ø> (-1.00%)	⬇️
social_core/backends/facebook_limited.py	62.50% <62.50%> (ø)
social_core/tests/backends/test_facebook.py	100.00% <100.00%> (ø)

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[atodorov]

AuthTokenError imported but unused, see failed CI jobs. Otherwise looks good to me.

[nijel]

Somehow I didn't have enabled pre-commit locally, pushed with the fixes now…