[pos] Add epoch argument to vp::pos::rewards

[joel-u410]

Describe your changes

This adds an epoch argument to the rewards() function in vp::pos. It does require a RPC node update in order to work, but it's backwards compatible. Tested with previous build of namadan and results are same as before:

With node on main and client on this branch:

$ ./target/debug/namadac rewards --source tnam1qrtypl0yazfamk8ptmgp608msl8wzrkpmqwppc7w --validator tnam1qxsx2ezu89gx252kwwluqp7hadyp285tkczhaqg0
Current rewards available for claim: 4625.955882 NAM

With both client and node on this branch:

$ ./target/debug/namadac rewards --source tnam1qrtypl0yazfamk8ptmgp608msl8wzrkpmqwppc7w --validator tnam1qxsx2ezu89gx252kwwluqp7hadyp285tkczhaqg0
Current rewards available for claim: 4625.955882 NAM

$ ./target/debug/namadac rewards --source tnam1qrtypl0yazfamk8ptmgp608msl8wzrkpmqwppc7w --validator tnam1qxsx2ezu89gx252kwwluqp7hadyp285tkczhaqg0 --epoch 60
Rewards for epoch 60: 4625.955882 NAM

$ ./target/debug/namadac rewards --source tnam1qrtypl0yazfamk8ptmgp608msl8wzrkpmqwppc7w --validator tnam1qxsx2ezu89gx252kwwluqp7hadyp285tkczhaqg0 --epoch 59
Rewards for epoch 59: 3887.536527 NAM

$ ./target/debug/namadac rewards --source tnam1qrtypl0yazfamk8ptmgp608msl8wzrkpmqwppc7w --validator tnam1qxsx2ezu89gx252kwwluqp7hadyp285tkczhaqg0 --epoch 58
Rewards for epoch 58: 3148.755426 NAM

Checklist before merging

• If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
  • This will require 2 reviewers to approve the changes
• If this PR requires changes to the docs or specs, a corresponding PR is opened in the namada-docs repo
  • Relevant PR if applies: (coming soon)
• If this PR affects services such as namada-indexer or namada-masp-indexer, a corresponding PR is opened in that repo
  • Relevant PR if applies: feat: backfill epoch rewards namada-indexer#235

[codecov]

Codecov Report

Attention: Patch coverage is 13.79310% with 50 lines in your changes missing coverage. Please review.

Project coverage is 74.42%. Comparing base (2ae305c) to head (89df61f).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/sdk/src/queries/vp/pos.rs	12.28%	50 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4196      +/-   ##
==========================================
- Coverage   74.46%   74.42%   -0.05%     
==========================================
  Files         342      342              
  Lines      107773   107826      +53     
==========================================
- Hits        80257    80252       -5     
- Misses      27516    27574      +58     

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[joel-u410]

Testing that this behaves as expected for a validator that claimed rewards in epoch 51:

$ ./target/debug/namadac rewards --validator tnam1qyf80vw4e8aa2efuk4jsg9lpwxrntsj2dql4tssa --epoch 50
Rewards for epoch 50: 2.179855 NAM

$ ./target/debug/namadac rewards --validator tnam1qyf80vw4e8aa2efuk4jsg9lpwxrntsj2dql4tssa --epoch 51
Rewards for epoch 51: 4.363707 NAM

$ ./target/debug/namadac rewards --validator tnam1qyf80vw4e8aa2efuk4jsg9lpwxrntsj2dql4tssa --epoch 52
Rewards for epoch 52: 2.897536 NAM

[joel-u410]

Of particular note, this code accounts for the rewards_counter when specifying an epoch by:

• Subtracting the current counter that was included by query_reward_tokens
• Adding the historical counter queried from storage at the height of epoch start

[brentstone]

Mind adding some unit tests here to demonstrate the behavior too @joel-u410?

[joel-u410]

Mind adding some unit tests here to demonstrate the behavior too @joel-u410?

For sure, I can look into that.