Unreliable reload_graphene_settings

`reload_graphene_settings` creates a new settings object, so settings imported via `from .settings import graphene_settings` don't get reloaded.

Start at the reload_graphene_settings entry point and trace how the settings object is created and imported through .settings. Check existing tests around settings reload behavior; done means a reference imported with `from .settings import graphene_settings` observes the reloaded settings rather than the old object.

索引モデルが issue の本文から書いたものです。