Multiple email support for EMU profiles

### Summary

Enterprise managed users will be able to maintain more than one email address in their user profile.

### Intended Outcome

Customers who maintain more than one domain due to business structure or acquisition are currently unable to maintain strong attribution to git history over time. GitHub notification routing may be impacted by changes to business structure.

### How will it work?

Enterprise managed users only support one email address being present in their user profiles. We will remove that limitation and add the ability to:
- attribute git commits from more than one email address to a specific EMU
- route notifications to more than one email address
- route notifications to a specific primary email address

To accomplish this, we will make updates to the SCIM APIs associated with user objects in order to support multiple email addresses. Email address data will come from the identity provider - Users will not be able to edit email addresses.