Resolve "Service Desk filter Error 500"

What does this MR do?

Fixes a NoMethodError caused by moving some code into the ::EE module in 9c2c1f3c

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Regression fix

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #3488 (closed)