TINKERPOP-3059: Prevent repeated option() calls to merge steps

[Iryna-Kahamlyk]

JIRA: https://issues.apache.org/jira/browse/TINKERPOP-3059

Summary

Prevented repeated option(onCreate), option(onMatch), option(outV) and option(inV) calls on mergeV() and mergeE(), which now throw an IllegalArgumentException instead of silently keeping only the last one.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 55.00000% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.96%. Comparing base (4722890) to head (7d453a0).
⚠️ Report is 159 commits behind head on 3.7-dev.

Files with missing lines	Patch %	Lines
...pache/tinkerpop/gremlin/jsr223/JavaTranslator.java	25.00%	6 Missing ⚠️
...che/tinkerpop/gremlin/features/StepDefinition.java	25.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             3.7-dev    #3714      +/-   ##
=============================================
+ Coverage      75.49%   75.96%   +0.46%     
- Complexity     13161    13325     +164     
=============================================
  Files           1092     1095       +3     
  Lines          67208    67586     +378     
  Branches        7391     7459      +68     
=============================================
+ Hits           50742    51339     +597     
+ Misses         13837    13588     -249     
- Partials        2629     2659      +30     

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[kenhuuu]

Change in semantics requires an update to docs/src/dev/provider/gremlin-semantics.asciidoc.

[kenhuuu]

The added unit tests are good and directly test the implemented fix however it doesn't actually test option(). What's needed to cover this are feature tests. In the 3.8-dev branch you can assert for errors during traversal construction due a small change in the test harness. I think you should backport that harness fix and add feature tests for this change.

[spmallette]

For committers - Created PR root bead: tp-ddu

🤖 Agent assisted comment.