Add external_authentication_uid to actors endpoint for querying

[kmacgugan]

No description provided.

[stevendanna]

Some minor nits:

• This prefers the email parameter over the external_auth_uid, while the Chef Server implementation is the other way around: oc_erchef users list: allow filtering by external_authentication_id chef-server#852
• The filtering code for email vs the new param is basically identical, maybe split it out into a function that takes the response and the field to filter by?

[srenatus]

@stevendanna I've updated the PR to address your concerns. :)

[stevendanna]

👍 Looks good to me.

[chefsalim]

👍