Limit Reporter field to customers added to the project

Issue Summary

When team managed project has the Service project access setting set to Customers added to this service project only by agents and admins, Agents still can set the Reporter field to customers who were not added to the project. 

Steps to Reproduce

1. Create a JSM project
2. Set Service project access  to Customers added to this service project only by agents and admins
3. Add ClientA to the project
4. As an agent. create a request, where you set the report to ClientB. The issue can be saved.
5. The Issue created in Step4 is not available to ClientB from the portal 

Expected Results

Only customers added to the project can be selected as Reporter on issues

Actual Results

All users added on the site level are available to choose from for the Reporter field.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available