Spike: Investigate current implementation for using optional interfaces

Overview

mod-users-bl currently declares two optional interface dependencies (See module descriptor).  While discussing MODUSERBL-153, it wasn't clear how the module handles this, or even if it works at all.

Scope

The following questions should be answered in scope of this spike:

• Does mod-users-bl (and stripes/ui-users) still work if these optional dependencies aren't enabled for the tenant?
  • both with an without the include and expandPermissions params
• How are permissions handled, specifically wrt OKAPI-1070, OKAPI-1090, FOLIO-3435, and other JIRAs related to undefined permissions.

Acceptance Criteria

• The questions above have been answered
• Spike findings have been documented (e.g. on the wiki)
• Additional user stories and/or spikes are created to as needed (e.g. in the case that bugs are discovered or this investigation raises new questions)