Fix Fossil delta construction in recovered publications

[FZambia]

This PR fixes wrong delta construction for recovered publications. The bug resulted into bad checksum errors on the client side. Also, added test for this.

PR also contains trace log improvements, we now handle json marshaling errors using fallback to protojson.

[codecov]

Codecov Report

Attention: Patch coverage is 69.23077% with 4 lines in your changes missing coverage. Please review.

Project coverage is 81.55%. Comparing base (f3e8061) to head (584666d).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
client.go	69.23%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #415      +/-   ##
==========================================
+ Coverage   81.38%   81.55%   +0.16%     
==========================================
  Files          40       40              
  Lines        7204     7210       +6     
==========================================
+ Hits         5863     5880      +17     
+ Misses        965      947      -18     
- Partials      376      383       +7     

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