feat: Allow multiple values for SSO attribute_requirements via comma separation

[meise]

In the current attribute_requirements implementation it is only possible to allow exact matching attribute values. Multiple allowed values for one attribute are not possible as described in #13238.

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[CLAassistant]

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[meise]

I'm not sure whether the current change is really ideal or whether the JSON schema should be changed to a value list.

[sandhose]

I would like to avoid changing the behaviour of existing configuration parameters, and instead introduce new parameters. I'd suggest one_of, values or in

Suggested change

	value: "sales,admins"
	one_off:
	- "sales"
	- "admins"

[meise]

Code has been adjusted accordingly.