By default, set the fullname from first+last and vice-versa

[dehnert]

Fixes #678.

Proposed changes

As described in #678 , when the SAML backend supplies a fullname, it's desirable for my Django user to have first_name and last_name set. This changes PSA so if fullname is set (in, eg, a SAML response) but not first_name/last_name, by default it generates a first_name and last_name automatically. Similarly, it does the reverse transformation when fullname is missing. IMO this is a net improvement, but obviously there's questions like "should this be enabled by default", "should it be in the default pipeline", etc. -- I'm happy to tweak this to make it fit the team's design goals better. Assuming the concept makes sense, I can write docs.

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[codecov]

Codecov Report

Merging #683 (3cfc739) into master (f27461d) will decrease coverage by 0.06%.
The diff coverage is 10.00%.

@@            Coverage Diff             @@
##           master     #683      +/-   ##
==========================================
- Coverage   77.01%   76.94%   -0.07%     
==========================================
  Files         319      319              
  Lines        9677     9687      +10     
  Branches     1036     1040       +4     
==========================================
+ Hits         7453     7454       +1     
- Misses       2072     2081       +9     
  Partials      152      152              

Flag	Coverage Δ
unittests	76.94% <10.00%> (-0.07%)	⬇️

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Impacted Files	Coverage Δ
social_core/pipeline/__init__.py	100.00% <ø> (ø)
social_core/pipeline/social_auth.py	78.18% <10.00%> (-15.16%)	⬇️

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[dehnert]

(I'll need to remove this, but I'd like to confirm that the general direction seems good before I do the cleanup.)

[dehnert]

Any thoughts on this general feature?