feat: add insecure flag

[JaeAeich]

Description

Add --insecure flag to login command.

• Fixes: Awkward Harbor login flow: Schema is mandatory. #9

Note the issue mentioned an awkward login flow when URL is given without https the client defaults to pretending the URL with localhost which causes the cli to err.

To consider

Other things to consider opening an issue for:

• Encrypting the password when store in ~/.harbor/config
• Removing password as flag from login command and take it as input discreetly.
• Currently flag --name isn't doing much, use to store multiple users and then use this config to easily login for different users, fix --name flag iverwritting the previously stored creds.

Current behaviour

 ./harbor login https://demo.goharbor.io -n jaeaeich -u admin -p Harbor12345 -i

@Vad1mo If the above mentioned issues seem reasonable maybe its worth opening issues for, do tell me so I can write further details.

[JaeAeich]

@Vad1mo @OrlinVasilev, can you have a look here, for the --insecure flag, I think this PR does that but maybe I can also push schema mandate issue in this or create another one. Please do let me know also what is the schema that you expected. I thought that if config is available and there is only one --name that should be take as default and login with that, otherwise ask the user for --name else if there is no config or it is incomplete ask the user for password and username.

[Vad1mo]

I'll look at it in more details in the next couple of days.