Embed digital objects into OAI using Atom feed.
Generate OAI API keys via user admin. refs #7469
Fixed issue with enabling OAI plugin. refs #7469
Process request only with OAI API key. refs #7469

Added a setting to disable OAI API key authentication

Added logic to require OAI requests provide key if an OAI
key exists and OAI key authentication is enabled. Sign in
user if correct OAI API key supplied so ACL checks in
template work.
Include about tag in OAI list output. refs #7468

Created a separate template for the about tag and made it so
the about tag is included in OAI-PHP output for the listRecords
verb (as well as getRecord).
Replaced primary key with slug. refs #7468

Replaced the use of a digital object's primary key with its
slug.
Allow OAI API auth if not required. refs #7469

If OAI API auth isn't required, allow requests to be made using
OAI API auth keys to get additional data (reflecting permissions
of user with matching auth key).