"tradable", "marginable", and "fractionable" move to the top level of global assets

Broker API

tradable, marginable, and fractionable are now top-level boolean properties on the GlobalAsset schema instead of string entries inside attributes. This matches the existing asset endpoints.

• attributes continues to carry the remaining attribute entries, such as has_options.
• Examples on the global asset endpoints have been updated to show the new placement and boolean values.

Affected Endpoints

• GET /v2beta1/assets
• GET /v2beta1/assets/{symbol_or_asset_id}