Change default marker to UUIDv4

[fliiiix]

Fixes #470

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 87.25%. Comparing base (084622e) to head (842c17a).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
radish/main.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #476   +/-   ##
=======================================
  Coverage   87.25%   87.25%           
=======================================
  Files          39       39           
  Lines        2377     2377           
=======================================
  Hits         2074     2074           
  Misses        303      303           

Flag	Coverage Δ
unittests	87.25% <66.66%> (ø)

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