Make.2-Atype entity = M.ttype entity is a type of authenticatable entity equal to MODEL.t
type strategy = (module Auth_sign.STRATEGY with type entity = entity)strategy is a function that authenticates an entity from a request.
val authenticate : 
  strategy Base.list ->
  Dream.request ->
  Static.AuthResult.t Dream.promiseauthenticate runs several authentication strategies for a request and defines, whether overall authentication was successful or not