use `ParseAuthorizedKey` instead of string parsing of the public key

[Xeckt]

Few changes in this pull request, more than anticipated:

• Remove publickey struct and use only ssh.publickey interface
• Taking advantage of the ssh.PublicKey Type() func to get a keys exact type for the publicKey struct:
• Removed the len check on how many fields were detected in the string, ParseAuthorizedKey func will detect if it's a valid key or not
• Changed the createtempfile func for testing to be more inclusive of it's intention, moved the dhcp string for testing to a constant in the daemon_test.go file
• moved ssh logic into it's own file with tests
• added helper functions for getting ssh strings

I hope all these changes are okay. Let me know if you would like to change anything or revert any of the changes. All tests have passed locally, including daemon tests.

[Xeckt]

Sorry for the title changes I borked up some stuff :D

On second consideration, it might be better to keep the struct field I changed to type as Algorithm

[Xeckt]

Thanks for the feedback! Will make the changes later today!

[Xeckt]

All changes and feedback resolved. Let me know if the new changes are ok!

[Xeckt]

Linter issues fixed, ran golangci-lint locally, seems all good.

[Xeckt]

Commits squashed!

[glimchb]

@Xeckt please note https://commitlint.js.org/ failing

[Xeckt]

Gah! Sorry!

[glimchb]

Gah! Sorry!

no worries. just add fix: or feat: in the start of the commit message and keep it lowercase...

[Xeckt]

Should be done now