TINKERPOP-3121 Prevent multiple by modulators or group count step

[andreachild]

https://issues.apache.org/jira/browse/TINKERPOP-3121

Prevent multiple by operators from being used for the group count step by throwing IllegalStateException if modulateBy is called more than once.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Please upload report for BASE (3.8-dev@c55d9cf). Learn more about missing BASE report.

Additional details and impacted files

@@            Coverage Diff             @@
##             3.8-dev    #3089   +/-   ##
==========================================
  Coverage           ?   76.33%           
  Complexity         ?    14017           
==========================================
  Files              ?     1104           
  Lines              ?    69654           
  Branches           ?     7507           
==========================================
  Hits               ?    53170           
  Misses             ?    13745           
  Partials           ?     2739           

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[kenhuuu]

Missing CHANGELOG entry. Also consider adding new semantics into reference documentation and/or provider documentation.

[kenhuuu]

VOTE +1

[andreachild]

Missing CHANGELOG entry. Also consider adding new semantics into reference documentation and/or provider documentation.

Thanks for catching this, added changelog and upgrade documentation.

[vkagamlyk]

VOTE+1

[Cole-Greer]

VOTE +1