Basic Groups support

[valerauko]

Why?

Support for SCIM user Groups is currently missing Closes #46

What?

• add options to configure how to handle Groups
• add API endpoints to deal with Groups

Caveats

• The PUT updating of Group members is a bit hacky.

Testing Notes

I'm developing this using Okta as well so there shouldn't be anything extra to set up.

• [x] sync Groups
• [x] update Group name (or similar mapped attribute)
• [x] update Group membership
• [x] delete Group (delete after unlink)

Todo

I'm planning to mark this "ready for review" once I add rspec tests and fix lint violations

Alternatives Considered

There is the option to build a more complete User association handling as outlined in #39, but I felt that's a bit too big to chew for this purpose.

[wernull]

@valerauko thanks for this PR! It looks like a lot of good stuff at first glance. We'll try to get to it some time this week

[wernull]

@valerauko sorry for the delay. Things have got a little busy and this is something we really want to put proper attention on

[valerauko]

No worries, take your time