Helpdesk tickets, subtasks for tickets, client connection

Hi,
We are testing the usability of the YouTrack system alongside other systems. In our company where more than 50 consultants work, we have roughly the same number of helpdesk agents. In addition to planning and executing SAP projects, we are testing whether we can manage support requests coming from our support clients with YouTrack. We examined the HelpDesk project in the free account we opened for testing, but we couldn't find much about how the helpdesk workflow should proceed. There is documentation for Helpdesk type projects, but we couldn't find answers to some of our questions there, or perhaps we weren't able to locate them.

There are a few priority issues:

• The users creating tickets via email or form, referred as "Reporters," these are employees of our clients. Multiple individuals (reporters) from a single client can open tickets. At the end of the month, we need to retrieve a ticket report based on each client. How will we establish the "Reporter->Client" connection, that is, where will we define our clients and their authorized ticket creators?
• When I want to open a sub-task for tasks that need to be done for a ticket coming to the Helpdesk-type project, I see that it doesn't have the sub-task creation feature like in other project types. What should I do to create tasks for a ticket? If I can create tasks for a ticket, I want to add a condition that all sub-tasks must be completed for the ticket to be closed.

Regards,

Bahri