Notify user if missing flag args on create account

[chasefleming]

Closes #1658

Description

Manual mode requires a key. Warn a user if they are missing the key flag before switching to interactive mode.

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For contributor use:

• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 33.97%. Comparing base (9d41db9) to head (72a6b86).

Files	Patch %	Lines
internal/accounts/create.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1668      +/-   ##
==========================================
- Coverage   33.97%   33.97%   -0.01%     
==========================================
  Files         100      100              
  Lines        6248     6251       +3     
==========================================
+ Hits         2123     2124       +1     
- Misses       3841     3844       +3     
+ Partials      284      283       -1     

Flag	Coverage Δ
unittests	33.97% <0.00%> (-0.01%)	⬇️

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