Use Custom Coverage (if exists) in EntitlementLog

Purpose:

In the entitlement log, if there is custom coverage available for an entry based on the Entitlement (Agreement Line), this should be used in the EntitlementLog entry coverage instead of the default PCI coverage

User story statement(s):

As a consumer of the EntitlementLog,
I want to have the correct coverage information
so that I can use it appropriately (e.g. in a union catalogue)

Scenarios:

1. Scenario:
   • Given an agreement line for a PCI with a custom coverage
   • When I view the EntitlementLog entry which has been created because of that custom coverage
   • Then the coverage statement will reflect the custom coverage OR be present alongside the default coverage with enough information for the consumer to differentiate and use the correct coverage

Dev task breakdown

https://github.com/folio-org/mod-agreements/blob/master/service/grails-app/views/entitlementLogEntry/_entitlementLogEntry.gson

This file currently creates the coverage summary manually, but perhaps can be tweaked to work a little more like:
https://github.com/folio-org/mod-agreements/blob/6febed3bee4aec20f1c2b97857ef51cabbbf710a/service/grails-app/views/entitlement/_entitlement.gson#L24-L36

• If entitlement.coverage exists, use that.
• Else do what it was doing before