555 fix pulling GitHub commits

[maciekbanas]

• handle GraphQL errors
• repeat request on 502 error (if httr2 retry does not work)
• fix building table out of commits output
• move repo cursor from query vars to function parameter

[codecov]

Codecov Report

Attention: Patch coverage is 84.09091% with 7 lines in your changes missing coverage. Please review.

Project coverage is 75.39%. Comparing base (b5907c3) to head (19a7a97).
Report is 6 commits behind head on devel.

Files with missing lines	Patch %	Lines
R/EngineGraphQLGitHub.R	80.55%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            devel     #558      +/-   ##
==========================================
- Coverage   75.46%   75.39%   -0.08%     
==========================================
  Files          17       17              
  Lines        3200     3219      +19     
==========================================
+ Hits         2415     2427      +12     
- Misses        785      792       +7     

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