Add has_pending_commit function to Group

[tomleavy]

Description of changes:

It is useful to be able to see that a commit is pending for a group

Testing:

Incorporated exercising this function into existing tests

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.52%. Comparing base (8f7d38b) to head (754a6b5).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #140   +/-   ##
=======================================
  Coverage   89.52%   89.52%           
=======================================
  Files         173      173           
  Lines       31450    31455    +5     
=======================================
+ Hits        28156    28161    +5     
  Misses       3294     3294           

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