DXCDT-602: Add help text to api cmd when no args passed

[sergiught]

🔧 Changes

Returns the help text when invoking the api cmd with no args.

📚 References

🔬 Testing

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (f9900b1) 72.50% compared to head (c71ec32) 72.48%.

Files	Patch %	Lines
internal/cli/api.go	25.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #914      +/-   ##
==========================================
- Coverage   72.50%   72.48%   -0.02%     
==========================================
  Files          93       93              
  Lines       12421    12424       +3     
==========================================
  Hits         9006     9006              
- Misses       2893     2895       +2     
- Partials      522      523       +1     

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