(2/3) Use Cobra, Koanf, and Ozzo rather than urfave/cli

[rtrox]

This PR depends on #110 -- please review and merge first, and I will rebase this PR

Description of the change

Sorry, I know this is a huge PR! It would have been way more work to try and move to Cobra and Koanf separately. This PR attempts to make no functional changes, and only refactor to new libraries. The libraries in question:

• Cobra (CLI)
• Koanf (Configuration)
• Ozzo (Validation)

Of course, I failed slightly at this -- I added Signal handling to the HTTP Server to shutdown gracefully when stopped.

Benefits

• Better Separation of Concerns - config logic now all happens in config, config logic has been removed from client.
• Simplified Command Flow - Each Command now only specifies the collectors which should run
• New Libraries - closes Refactor: Switch to koanf & cobra for config & CLI library #58
• Stronger Validation - ozzo provides well formed validation rules, to test for valid IPs, URLs, regex, etc with a simpler interface.

Possible drawbacks

It's just a big PR :-(

Applicable issues

• fixes Refactor: Switch to koanf & cobra for config & CLI library #58

Additional information

[onedr0p]

You are a machine! I am giving this a solid look thru but overall looks very solid!

My fingers are going to fall off typing up the release notes for v2.0.0 😄

[onedr0p]

My only concern with using ozzo is its current maintained state.

go-ozzo/ozzo-validation#162

It's not a huge problem but I did see some more active libraries:

• https://github.com/gookit/validate
• https://github.com/asaskevich/govalidator

[rtrox]

oof, good catch! I totally missed that >.< I've been using it in other projects, looks like I have some updating to do :-D

Bummer that it's no longer maintained, it had a super clean interface. It looks like some folks are trying to revive it in a fork, but it was announced 3 weeks ago, which is coincidentally also it's last commit. Probably want to let that one bake a bit before counting on it.

I'll take a look at the interfaces of the libraries you linked and work on updating this.

[rtrox]

I just updated this to 1) rebase, and 2) move to gookit/validate rather than ozzo.

[onedr0p]

I spent some time reviewing the branch this morning and I'm very impressed!