Support single and multi value attributes

[SxDx]

I think it is essential to handle both single and multi value attributes as Identity Providers often send
responses containing both types, e.g. single for email and multi for roles.

I have provided an example of the new attribute map yaml. The type is configureable per attribute.

The change is not backwards compatible but it would be relatively easy to add if it is a
blocking issue.

[adamstegman]

Thanks for making this change! This looks great, but I have two requests:

• like you said, backwards compatibility will mean I can merge this—we have no immediate plans for a breaking version
• unit tests for the new functionality

Thanks again!

[adamstegman]

I'd prefer something a little more explicit:

Suggested change

	@attributes.send(config["attribute_type"], String(key))
	case config["attribute_type"]
	when "single"
	@attributes.single(String(key))
	when "multi"
	@attributes.multi(String(key))
	end

[adamstegman]

I fixed the tests on master, so you should also merge/rebase master again.

[victorlcampos]

Hi Guys,
any update about this PR? It will help a lot here =)

[khuong-acorns]

Bumping to see if there's any plans to include this as well. Having multiple attribute values for roles would be a big plus

[Taeir]

I think this would be quite a valuable addition, but perhaps the way it is done should be changed a bit to be compatible with current setups without having to change the existing yml files for single value attributes. May look into making a PR for that if I find a good way to do it.

[doconnor-clintel]

I would benefit greatly from this as a v2.0.0 and breaking change.

[doconnor-clintel]

#245 fixes tests, add coverage.