Support optional result indication when accepting an approval request

[matthewwalsh0]

Description

Update the accept method of the ApprovalController to return a promise which optionally only resolves once the approval request creator has indicated the success or failure of any post-approval logic.

This is achieved using callbacks optionally provided in the approval request promise.

This is necessary to support more complex approval flows in which the request acceptor, typically a client frontend, must know the success of the resulting logic, or must receive some resulting data.

Changes

• ADDED: waitForResult option to accept method to resolve new promise when success or failure is indicated.
• ADDED: expectsResult option to add and addAndShowApprovalRequest method to change the resolved promise to return a result object including the value and new resultCallbacks.
• ADDED: expectsResult property to ApprovalRequest to store return type preference in state.
• ADDED: Associated types including AddResult, AcceptResult, AcceptResultCallbacks, and AcceptOptions.

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation for new or updated code as appropriate (note: this will usually be JSDoc)
• I've highlighted breaking changes using the "BREAKING" category above as appropriate