Add needed permission for Exchange OAuth

[YetAnotherGerrit]

We list all permissions needed for M365-E-Mail-Channel and M365-3d-Party-Authentication, but not for Exchange-OAuth:

https://admin-docs.zammad.org/en/latest/system/integrations/exchange.html

We need something similar to that or that for Exchange OAuth as well.

[ralf401]

@YetAnotherGerrit Ok now after adding my first comment, I saw that this is a dropdown where you can choose OAuth. Sorry I overlooked it :-)

I'll try to add an explanation for that.