Gitlab.TokenAuthentication Token for accessing GitLab APIs.
Of the several ways provided in GitLab, we currently support:
val create_url : 
  client_id:string ->
  redirect_uri:Uri.t ->
  state:string ->
  scopes:Gitlab_t.scope list ->
  unit ->
  Uri.tCreate URL for Authorisation code flow. https://docs.gitlab.com/ee/api/oauth2.html#authorization-code-flow
val of_code : 
  client_id:string ->
  client_secret:string ->
  ?grant_type:grant_type ->
  redirect_uri:string ->
  code:string ->
  unit ->
  t option Lwt.tRetrieve an OAuth Token using the default grant_type AuthorizationCode. Use the refresh_token along with a grant_type of RefreshToken to request a refreshed OAuth Token.
val of_string : string -> tof_string create an AccessToken.
val to_string : t -> stringto_string token is the string serialization of token.