add login command

[amartin120]

Please check below, if the PR fulfills these requirements:

• The commit message follows the guidelines.
• Tests for the changes have been added (for bug fixes / features).
• Docs have been added / updated (for bug fixes / features).

What kind of change does this PR introduce?

• adds login command.

What is the current behavior?

• Currently, before dealing with authenticated registries via hauler store add/sync you need to do a docker/cosign login prior to issuing those commands.

What is the new behavior (if this is a feature change)?

• hauler login has been added meaning you still have to run a login command, but now it's just part of the hauler toolset.

❯ hauler login harbor.amartin.cloud -u <user> -p <password>                                                                                                                                                                                                                                                    
4:03PM INF logged in via /Users/amartin/.docker/config.json

Does this PR introduce a breaking change?

• Shouldn't.

Other information:

[zackbradys]

Hey @amartin120. What is the error message when trying to hauler store add image or hauler store copy when users don't or forget to authenticate with the registry?

[amartin120]

@zackbradys

❯ ./bin/hauler store copy registry://harbor.test.cloud                                                                                                                                                                                                                                                   
8:10AM INF hauler/rancher:2.8.2
8:10AM ERR Error: remote write: HEAD https://harbor.test.cloud/v2/hauler/rancher/manifests/2.8.2: unexpected status code 401 Unauthorized (HEAD responses have no body, use GET for details)
8:10AM ERR main.go:74: error during command execution: remote write: HEAD https://harbor.test.cloud/v2/hauler/rancher/manifests/2.8.2: unexpected status code 401 Unauthorized (HEAD responses have no body, use GET for details)
Error: exit status 1

[zackbradys]

LGTM!!