Not possible to specify `account_selection` when initialising session for requisition

[MattiaPeiretti]

Describe the bug
Cannot add 'account_selection' flag via the SDK. Although it is possible to find it in the API docs

https://developer.gocardless.com/bank-account-data/endpoints

To Reproduce
Steps to reproduce the behavior:
POST /requisitions

Expected behavior
Possible to pass flag

Screenshots

Sourcecode is missing the flag...

If you're having general trouble with your Nordigen integration or bank related issue, please reach out to our support via email bank-account-data-support@gocardless.com

Matt from PocketCFO

[MattiaPeiretti]

Testing change in light of recent pull request