implement distribution spec auth interface

[guacamole]

AccessController interface in distribution spec which allows us to AuthN/AuthZ. This makes implementing authentication for OpenRegistry simpler and make sure that we don't miss any steps or APIs

Following are the snippets from distribution implementation:

// AccessController controls access to registry resources based on a request
// and required access levels for a request. Implementations can support both
// complete denial and http authorization challenges.
type AccessController interface {
	// Authorized returns a non-nil error if the context is granted access and
	// returns a new authorized context. If one or more Access structs are
	// provided, the requested access will be compared with what is available
	// to the context. The given context will contain a "http.request" key with
	// a `*http.Request` value. If the error is non-nil, access should always
	// be denied. The error may be of type Challenge, in which case the caller
	// may have the Challenge handle the request or choose what action to take
	// based on the Challenge header or response status. The returned context
	// object should have a "auth.user" value set to a UserInfo struct.
	Authorized(ctx context.Context, access ...Access) (context.Context, error)
}

// CredentialAuthenticator is an object which is able to authenticate credentials
type CredentialAuthenticator interface {
	AuthenticateUser(username, password string) error
}

// Challenge is a special error type which is used for HTTP 401 Unauthorized
// responses and is able to write the response with WWW-Authenticate challenge
// header values based on the error.
type Challenge interface {
	error

	// SetHeaders prepares the request to conduct a challenge response by
	// adding the an HTTP challenge header on the response message. Callers
	// are expected to set the appropriate HTTP status code (e.g. 401)
	// themselves.
	SetHeaders(r *http.Request, w http.ResponseWriter)
}

for implementation reference check https://github.com/distribution/distribution/blob/main/registry/auth/auth.go