Store auth token in a cookie

[hackerwins]

Description:

Store auth token in a cookie.

We implemented the login in #31 but we store the auth token in localStorage.

Since localStorage can be referenced by JavaScript, storing the token in a cookie is recommended.

Let's store the auth token in a cookie.

Why:

• LocalStorage/SessionStorage is vulnerable to XXS attacks.

[chacha912]

There are additional considerations in this issue.

The current Dashboard network structure is as follows.
(ref: https://github.com/yorkie-team/dashboard#how-dashboard-works)

• The auth token is transmitted as a cookie from the gRPC server. At this point, set the httpOnly and secure options.
• The gRPC-web client checks that the cookie is transmitted correctly.
• After checking that the cookie is set in the browser, Change the login status in the homepage header.