apis: add protobuf for reservation

[zwzhang0107]

Ⅰ. Describe what this PR does

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how to verify it

Ⅳ. Special notes for reviews

V. Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests
• All checks passed in make test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.68%. Comparing base (18ba907) to head (a5b9f8e).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2192      +/-   ##
==========================================
- Coverage   67.68%   67.68%   -0.01%     
==========================================
  Files         446      446              
  Lines       42694    42694              
==========================================
- Hits        28899    28896       -3     
- Misses      11275    11276       +1     
- Partials     2520     2522       +2     

Flag	Coverage Δ
unittests	67.68% <ø> (-0.01%)	⬇️

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[hormes]

/lgtm
/approve

[koordinator-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hormes

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• apis/OWNERS [hormes]

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