[ISSUE-897] Add ANONYMOUS Permission

[seonWKim]

Motivation

If there is no sensitive information in a repository, users may want to make the repo public and allow access without an access token. ANONYMOUS could be added as a new permission in addition to OWNER, MEMBMER and GUEST.

Modification

• Add ProjectRole#ANONYMOUS
• Modify UI

Result

• Users will be able to add ANONYMOUS role to their project

Help

• Token is verified by Authorizer implementations(ApplicationTokenAuthorizer, CsrfTokenAuthorizer, SessionTokenAuthorizer). The Authorizer implementations always checks whether token == null, so requests without access token will always fail. I wonder how we can allow anonymous users to access public repositories(without passing access token) with the Authorizer's token checking logic.

Links

https://github.com/line/centraldogma/issues/897