Fix #366: Export PromoteNewMaster, handle sequence zero

[Kaustubh1204]

• Exported promoteNewMaster method to PromoteNewMaster to fix build error
• Fixed failover validation to allow sequence == 0 when master is also 0
• Resolves issue Failover failed because of sequence is 0 #366 where failover failed with empty shards

[git-hulk]

@Kaustubh1204 Thanks for your contribution.

Exported promoteNewMaster method to PromoteNewMaster to fix build error

I cannot see when the build error, could you please elaborate a bit?

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 49.23%. Comparing base (6c56470) to head (43766bd).
⚠️ Report is 104 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable     #373      +/-   ##
============================================
+ Coverage     43.38%   49.23%   +5.84%     
============================================
  Files            37       45       +8     
  Lines          2971     3790     +819     
============================================
+ Hits           1289     1866     +577     
- Misses         1544     1716     +172     
- Partials        138      208      +70     

Flag	Coverage Δ
unittests	49.23% <100.00%> (+5.84%)	⬆️

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[greatsharp]

@Kaustubh1204 good job!

[Kaustubh1204]

Hi @git-hulk, thanks for reviewing!

The build error occurred because the method promoteNewMaster was defined in its module but was not exported. When other parts of the code tried to import it, the build failed with an error like “undefined” or “cannot find module export.”

By exporting it as PromoteNewMaster, it can now be properly imported and used across the codebase, which resolves the build failure.

Additionally, the failover validation logic was updated to allow sequence == 0 when the current master’s sequence is also 0. This addresses the issue reported by @original-author in #366 (“Failover failed because of sequence is 0”), where failover would fail for empty shards. Now, the failover process can correctly handle cases where both the current master and the new master have a sequence of 0.

These two changes together ensure that the build succeeds and that failover behaves correctly in all edge cases.

[git-hulk]

@Kaustubh1204 promoteNewMaster is used inside the store package, so it's unnecessary to export.