Bug: ACAPY_MEDIATION_OPEN env var not working as expected

[wip-abramson]

I have moved to passing all agent configuration in through an .env file. However, when trying to set mediation using this argument, which does seem to be correct from the argparse file in acapy mediation requests are not being automatically granted.

I have changed to use the --open-mediation flag in a startup script instead.

I had a little dig into the ACA-Py code but couldn't spot anything obvious.

It is possible this is an issue on my end still, but I am setting all other args on agent the same way so seems unlikely.