Refactor CLI to use Cobra

[calvinmclean]

Refactoring the API to use Cobra which will make it easier to add better subcommand structure and flags. It will also make the CLI more extendable.

Remaining TODOs (or create separate issue to track):

• Combine address and bindAddress to use the same var and flag name, but they will have separate defaults and descriptions since they are part of different subcommands
• Add API modifier method to add custom subcommands to a CLI (Allow adding custom subcommands #53)
• Add subcommand and flags for a "raw request" that doesn't require interacting with a Resource (Add subcommand and flags for a "raw request" that doesn't require interacting with a Resource #54)
• Change request body to be a flag for Post, Put, and Patch instead of positional argument
• Add flag to read request body from file just use cat I think...
• Change parent IDs to be a flag instead of positional and add validation to CLI for better documentation (also look into creating custom flags depending on Client parents names)
• Use strings.ToLower() for client names as subcommands ("todos" instead of "TODOs" on CLI). Or use cobra.EnableCaseInsensitive
• CommandLineTest is not very useful since it doesn't parse the actual args and still requires setting body, query, etc.

[codecov]

Codecov Report

Merging #52 (7a84596) into main (f025139) will decrease coverage by 0.67%.
The diff coverage is 88.73%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #52      +/-   ##
==========================================
- Coverage   81.00%   80.33%   -0.67%     
==========================================
  Files          23       23              
  Lines        1179     1246      +67     
==========================================
+ Hits          955     1001      +46     
- Misses        150      162      +12     
- Partials       74       83       +9