Allow an array of enum values

[trisch-me]

Is your feature request related to a problem? Please describe.
Currently the type of attribute is limited to the simple values (int, string etc) or array of it. For some of the fields we might need to have a predefined list of values (enum) and to be able to have an array of them - array of enum values.

Describe the solution you'd like
I propose to add a possibility to have an array of enum values for group attributes

Additional context
This was brought in file PR but I believe might be interesting for other cases as well