List users who can be assigned to issues in a specific project. The project_key, query filter, and vendor_id semantics are vendor-specific (e.g., for Jira: vendor_id is the accountId, query filters by name or email).
Vendor project identifier. Use the vendor_id from the list projects response.
Vendor-specific user filter string. For Jira: filters by display name or email address. Omit to return all assignable users for the project.
1 <= x <= 500x >= 0