\Drupal\entity_usage\UrlToEntity::makeUrlRelative() does ensure the configured site domain is actually the host

Problem/Motivation

makeUrlRelative host-pattern does not anchor to the host boundary, so subdomains and other sites containing the domain string match.

For site domain example.com, the regex built is /example\\.com\\//. Applied as a substring match against the full URL, this matches https://subdomain.example.com/node/42 (host contains example.com/). The URL is treated as local and entity usage for /node/42 is recorded, even though the link points to a different host

Steps to reproduce

Proposed resolution

• Change site_domains config to split out the config into host and path
• Update UrlToEntity to use new config
• Fix old config via an update hook
• Handle IDNs (domains with unicode in them)

Remaining tasks

User interface changes

API changes

Data model changes