[Helpdesk] Improve interface for helpdesk managers

Feature Request

Description

Changes to the helpdesk (https://scipost.org/helpdesk/) interface to improve workflows.

Tasks

• Add Defined by field pointing to the profile that opened the ticket

• Add filter, search and ordering options. Ordering by: Defined on, Defined by, Priority, Status, and Latest activity; both ascending and descending ordering options. Filter by: status, priority and assigned to. Search on: title, defined by, id of associated object (e.g., submission id if Re: field has content).

• Progress field is empty. What was meant to be here? Either display the data or remove field.

• "Awaiting response from SciPost" status should have another colour, not the same green as awaiting response from user. Maybe orange or yellow.