Sandbox: Gov-Test-Scenario header QUARTERLY_OBS_01_OPEN causes 500 Internal Server Error

[abcsa-dev]

API

Describe the bug
Currently, if a Gov-Test-Scenario header value of QUARTERLY_OBS_01_OPEN is sent to the /organisations/vat/{vrn}/obligations endpoint, a "500 Internal Server Error: An internal server error occurred" response is sent back.

That header could previously be sent - though I've not used sandbox for some time, so I don't know when this issue started.

To Reproduce
Send QUARTERLY_OBS_01_OPEN as the Gov-Test-Scenario header value in a call to/organisations/vat/{vrn}/obligations endpoint

Expected behavior
A successful response with (test) obligations data