The current Wikibase\Repo\Domains\Reuse\Infrastructure\GraphQL\GraphQLService class has grown large and is becoming difficult to navigate, read, and modify. It currently mixes multiple concerns in a single class:

• core service
• validation logic T419008 (?)
• tracking T418558
• error logging T419008

These mixed concerns should be seperated.

AC:

• Service logic, validation, and tracking are separated if possible
• The codebase is easier to navigate and extend
• Behavior remains unchanged