… best height
## Issue being fixed or feature implemented
Platform wants to know the height of the bestchainlock when they call
submitchainlock; sooo we change the API of submitchainlock to also
return the height
## What was done?
Adjust API and tests
## How Has This Been Tested?
New tests added for this behavior
## Breaking Changes
Not really any; I **guess** that return value could be considered
breaking change; but going from nothing -> something feels unlikely to
break anything although it in theory could.
## Checklist:
_Go over all the following points, and put an `x` in all the boxes that
apply._
- [ ] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have added or updated relevant unit/integration/functional/e2e
tests
- [ ] I have made corresponding changes to the documentation
- [x] I have assigned this pull request to a milestone _(for repository
code-owners and collaborators only)_
---------
Co-authored-by: UdjinM6 <UdjinM6@users.noreply.github.com>
Co-authored-by: Konstantin Akimov <knstqq@gmail.com>
