Check client Sequence while pushpulled

[humdrum]

What this PR does / why we need it:

• Add sequence validation logic.
  • When process push changes, the client sequence has to be prevClientSeq + 1
  • If the client sends an invalid ServerSeq, Send a snapshot so that the client can try to fix it.
• Preserve sequence numbers for the push-pull response of detach and remove API.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Additional documentation:

Checklist:

• Added relevant tests or not required
• Didn't break anything

[codecov]

Codecov Report

Merging #503 (055f5ce) into main (fdd62a9) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #503      +/-   ##
==========================================
- Coverage   48.60%   48.60%   -0.01%     
==========================================
  Files          69       69              
  Lines        5919     5915       -4     
==========================================
- Hits         2877     2875       -2     
+ Misses       2696     2694       -2     
  Partials      346      346              

Impacted Files	Coverage Δ
server/backend/database/client_info.go	68.42% <ø> (+0.92%)	⬆️

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[hackerwins]

I think we need a simple design on how to deal with this issue. For now, I will register a separate issue and close this PR. #805