bug: returns appDataHash

[mfw78]

Problem

A typedoc issue: https://github.com/cowprotocol/cow-sdk/blame/c73a93e2a4ba056611413b56210a77554b289b10/src/order-book/api.ts#L339.

Solution

This API actually returns the appDataHash and should be annotated as such.

[mfw78]

Further to this:

uploadAppData returns an AppDataObject but AppDataObject has fullAppData, but the uploadAppData only returns the appDataHash (from the actual API), whereas the getAppData returns an AppDataObject which actually contains the fullAppData document (ie. the JSON-stringified version of the app data document).