eholdings app: Validate user access to eholdings and affiliated EBSCO KB credentials.

As a FOLIO System Admin that manages multiple EBSCO KBs in one tenant
I must assign a user to one EBSCO KB credentials
So that the user gets to access to the eholdings s/he manage

General Requirements

• If a library has only one EBSCO KB credentials configured then it is not required for them to assign users.
• This requirement only applies to a tenant that has configured multiple EBSCO KB credentials
• The user can only be assigned to one set of EBSCO KB credentials.
• If multiple EBSCO KBs have been configured and a user has not been assigned to a set of EBSCO KB credentials then s/he will not get access to the eHoldings app regardless of assigned eholdings permissions

Acceptance Criteria

Given I have already created one set of EBSCO KB credentials prior to this development work
And I have assigned eholdings permissions
When I click on the eholdings app
Then no change to what I can do in the eholdings app

Given I have created only one set of EBSCO KB credentials
When I Edit Settings > eholdings > Knowledge base
AND I assign a user
Then only the users assigned to the knowledge base
With the assigned eholdings app permissions will have access to the eholdings app

Given I have created multiple EBSCO KB credentials
When I assign a user to a set of EBSCO KB credentials
AND s/he has been assigned eholdings permissions
Then s/he has access to the eholdings tied to that set of EBSCO KB credentials