Allows an address book config data type to be added for the global config.

Fixes openemr#6752

Adds an endpoint for retrieving users from the system.  If there are
users we wish to retrieve that are not practitioners (such as external
entities that are in the address book), we can't use the practitioner
api.  Instead we expose the users endpoint.

Fixes openemr#6751

After conversations with admins we decided to go with a relative api url
for the internal api usage instead of the oauth2 full path.

Also fixed a path issue.