fix: allow groups of groups of transactions

[kieranroneill]

Description

Please explain the changes you made here

The Kibisis client was not handling the case when groups of groups of transactions were being sent.

This fix attempts to rectify this by flattening the transactions before they are transmitted to the Kibisis wallet.

Checklist

Please, make sure to comply with the checklist below before expecting review

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary

[drichar]

This is the error I get now when I try signing and sending the test transaction in Storybook:

[kieranroneill]

This fix is part of the wider Kibisis client overhaul in #174