Improve unboxing

[amotl]

About

This patch includes various improvements that are useful when using the program without knowning much about its parameters and invocation capabilities.

Details

• Options: Permit usage without authentication credentials or token
• Options: Do not assume defaults for ACTION and --grafana_label args
• Options: Print help text when using erroneous parameters
• Options: Print help text when using erroneous parameters
• Documentation: Add "Synopsis" section to README

References

• Exception when invoked without arguments #30

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 69.41%. Comparing base (0c1dad4) to head (c046340).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
grafana_import/cli.py	75.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #34      +/-   ##
==========================================
+ Coverage   68.91%   69.41%   +0.50%     
==========================================
  Files           5        5              
  Lines         444      448       +4     
==========================================
+ Hits          306      311       +5     
+ Misses        138      137       -1     

Flag	Coverage Δ
unittests	69.41% <75.00%> (+0.50%)	⬆️

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