`ApiSettings.api_extension_is_enabled` method doesn't exist!

[vincentsarago]

stac-fastapi/stac_fastapi/api/stac_fastapi/api/openapi.py

Line 76 in c55c253

if settings.api_extension_is_enabled(ApiExtensions.fields):

@geospatial-jeff I can't find this method after 1.0 😁 https://github.com/stac-utils/stac-fastapi/blame/1.0.0/stac_api/config.py#L80-L86

[vincentsarago]

the config_openapi method is deprecated 😅

#523