Reduce utils.Cfg references (#7650)

* app.UpdateConfig method

* test fix

* another test fix

* the config override option as-was is just error prone, remove it for now

* derp

api4/oauth.go

@@ -313,7 +313,7 @@ func deauthorizeOAuthApp(c *Context, w http.ResponseWriter, r *http.Request) {
 }
 
 func authorizeOAuthPage(c *Context, w http.ResponseWriter, r *http.Request) {
-	if !utils.Cfg.ServiceSettings.EnableOAuthServiceProvider {
+	if !c.App.Config().ServiceSettings.EnableOAuthServiceProvider {
 		err := model.NewAppError("authorizeOAuth", "api.oauth.authorize_oauth.disabled.app_error", nil, "", http.StatusNotImplemented)
 		utils.RenderWebError(err, w, r)
 		return
@@ -560,7 +560,7 @@ func signupWithOAuth(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	if !utils.Cfg.TeamSettings.EnableUserCreation {
+	if !c.App.Config().TeamSettings.EnableUserCreation {
 		c.Err = model.NewAppError("signupWithOAuth", "api.oauth.singup_with_oauth.disabled.app_error", nil, "", http.StatusNotImplemented)
 		return
 	}