[RFS] Use shard routing from source while bulk indexing.

[kanatti]

Description

• Category - Bug Fix
• Why these changes are required? Not using routing from source breaks routing based queries on target index.
• What is the old behavior before changes and new behavior after changes? Old behavior was creating target docs without routing. New behaviour creates target docs with routing.

Issues Resolved

#1162

Is this a backport?
No

Testing

1. Updated unit tests for BulkDocSection
2. Updated EndToEndTest to verify routing
3. Manually tested with ES 6.8

Note: I will raise followup PR with test-resource snapshot with routing along with updated tests for LuceneDocumentsReaderTest

Check List

• New functionality includes testing
  • All tests pass, including unit test, integration test and doctest
• New functionality has been documented
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[AndreKurait]

Thanks for taking the time for this feature add and tests.

Implementation looks good, the testing comment shouldn't be too much work to modify then we should be good to go.

[AndreKurait]

Thanks for adding this function, though we are missing any assertion on the doc with routing on shard 2.

Can we take in indexName, queryString, and _routing as parameters to this function and return the hits?

Then we can do the assertion in the test above.

This function can also be moved to SourceTestBase

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.76%. Comparing base (6217e1c) to head (b5a21d6).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #1164   +/-   ##
=========================================
  Coverage     80.76%   80.76%           
- Complexity     2948     2951    +3     
=========================================
  Files           400      400           
  Lines         15104    15111    +7     
  Branches       1021     1021           
=========================================
+ Hits          12199    12205    +6     
  Misses         2288     2288           
- Partials        617      618    +1     

Flag	Coverage Δ
unittests	80.76% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[AndreKurait]

Since the new code path is tested, merging this in and the testing refactor can be addressed in a followup PR