enable saml for RN app (#5635)

* enable saml for RN app

* remove unnecessary user sanitize

api/user.go

@@ -1451,9 +1451,14 @@ func completeSaml(c *Context, w http.ResponseWriter, r *http.Request) {
 			http.Redirect(w, r, c.GetSiteURL()+val, http.StatusFound)
 			return
 		}
+
+		if action == "mobile" {
+			w.Write([]byte(""))
+		} else {
 			http.Redirect(w, r, app.GetProtocol(r)+"://"+r.Host, http.StatusFound)
 		}
 	}
+}
 
 func userTyping(req *model.WebSocketRequest) (map[string]interface{}, *model.AppError) {
 	var ok bool