feat: Add a command to authenticate with Schemathesis.io

[Stranger6667]

Token is not used yet for the SaaS integration

[codecov-commenter]

Codecov Report

Merging #1403 (1824c25) into master (ccb4191) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1403   +/-   ##
=======================================
  Coverage   99.18%   99.19%           
=======================================
  Files          83       84    +1     
  Lines        6418     6458   +40     
  Branches     1132     1135    +3     
=======================================
+ Hits         6366     6406   +40     
  Misses         26       26           
  Partials       26       26           

Flag	Coverage Δ
unittests	99.16% <100.00%> (+<0.01%)	⬆️

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Impacted Files	Coverage Δ
src/schemathesis/cli/__init__.py	99.07% <100.00%> (+0.02%)	⬆️
src/schemathesis/service/__init__.py	100.00% <100.00%> (ø)
src/schemathesis/service/constants.py	100.00% <100.00%> (ø)
src/schemathesis/service/hosts.py	100.00% <100.00%> (ø)

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