Support for entity usage

Problem/Motivation

When someone links to a document via this module's vanity redirect path /document/[id], we want that recorded as a usage of the document in the Entity Usage module. Right now it's not registered as a usage.

Steps to reproduce

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Proposed resolution

Implement event subscriber for the URL_TO_ENTITY event from the Entity Usage module. If the URL matches our pattern, return a usage for the entity ID.

Remaining tasks

User interface changes

API changes

Data model changes