Add logout command to CLI

[hackerwins]

Description:

We can log in to the Yorkie server, to use admin APIs which can manage documents and projects with CLI.

$ yorkie login -u username -p password
$ yorkie project ls

 NAME     PUBLIC KEY            SECRET KEY            AUTH WEBHOOK URL  AUTH WEBHOOK METHODS  CREATED AT
 default  cg044avhiqss73d20n2g  cg044avhiqss73d20n30                    []                    6 days

But we don't have logout command to log out from the Yorkie server yet.

Refer to:

• docker login: https://docs.docker.com/engine/reference/commandline/login/
• docker logout: https://docs.docker.com/engine/reference/commandline/logout/
• Allows only authenticated users to use the cluster's admin commands #377

Related to #544

Why:

• The user can use the logout command to delete authentication information locally.

[blurfx]

I'm interested in this issue. can I work on it?

[blurfx]

I'm working on a logout CLI command, but I currently have the following issues and would like to discuss them.

We currently use JWT for authentication, so we can't invalidate them.

So this is my approach.

• Give the JWT token a unique id using jti field
• Record the token id somewhere when a user requests to log out. (to mark that the token id has been invalidated)
  • It should also work in cluster mode, so something like Redis would be good.
• Within the TokenManager.Verify function, or wherever the function is used, check if the token has been marked as invalidated using Redis. (if Redis has a token id, it's invalidated)

I tried the above method, but there were two problems.

• I created a Server.LogOut method in server/admin.go, but couldn't find a way to get the token when request has come.
• I couldn't find a way to access Redis or similar storage on the Yorkie server. (I don't even know if it exists)

Please let me know if you can think of a better approach, or if there's a way to work around the two issues above. :)

[hackerwins]

Thank you for your research.

Instead of token invalidation, I think deleting the token from the context file(~/.yorkie/config.json) would be a more appropriate way to handle the logout command for now.

It might be beneficial to consider aspects such as token invalidation for future reference as well.