API: Flag "user" parameters in various modules as type 'user'

API: Flag "user" parameters in various modules as type 'user'

The API 'user' type accepts both user names and IP addresses, and
applies normalization but not canonicalization. We should be using this
on basically every user parameter to ensure that e.g. IPv6 usernames get
uppercased.

Bug: T122803
Change-Id: Ic67fb54061ac311e54f325b2a1a4658f43b8fef4