align block header with protobuf schema

[illia-malachyn]

Closes: #765

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 81.81818% with 24 lines in your changes missing coverage. Please review.

Project coverage is 57.04%. Comparing base (3ae9ebc) to head (9f84549).
Report is 14 commits behind head on master.

Files with missing lines	Patch %	Lines
access/grpc/convert/convert.go	76.00%	16 Missing and 8 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #778      +/-   ##
==========================================
+ Coverage   56.65%   57.04%   +0.39%     
==========================================
  Files          35       35              
  Lines        7269     7391     +122     
==========================================
+ Hits         4118     4216      +98     
- Misses       2657     2673      +16     
- Partials      494      502       +8     

Flag	Coverage Δ
unittests	57.04% <81.81%> (+0.39%)	⬆️

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