Add service desk information to project graphQL endpoint

What does this MR do?

It adds information about service desk enablement and its address to the project graphql endpoint.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Related issue: #34261 (closed)