Filtering rack reservations by username raises ValueError

[jeremystretch]

Environment

• Python version: 3.6.9
• NetBox version: 2.10.1

Steps to Reproduce

1. Create one or more rack reservations
2. Attempt to filter the reservations by username, e.g. GET /api/dcim/rack-reservations/?user=jstretch

Expected Behavior

NetBox should return only the reservations assigned to the specified user.

Observed Behavior

A ValueError exception is raised because the user filter is incorrectly defined on RackFilterSet.