Add parameter to pass in a list of Role names for use in export

[tim-d-blue]

This provides a simpler method to combine multiple roles on export. Given a simple list of roles, when export is called a list of roles can be provided and the export will combine the roles and filter fields appropriately. Therefore dynamic role combination is available. Blacklist roles will override whitelist roles.

[bintoro]

I like the idea, but couldn't we repurpose the existing role parameter instead of introducing a parallel parameter roles?

Something like:

if isinstance(role, Role):
    role = (role,)

and then the rest of the code could just assume it's an iterable of roles.

Btw, the __name__ attribute on functions has been around at least since Python 2.5, so I'm thinking this whole thing:

if role and ((hasattr(role.function, "func_name") and
              role.function.func_name == "whitelist")
             or (hasattr(role.function, "__name__") and
                 role.function.__name__ == "whitelist")):

can probably be simplified to:

if role and role.function.__name__ == "whitelist"

[berislavlopac]

Any updates on this PR?

[lkraider]

Needs to be refactored according to suggestions before pulling it in.