[Bug] api for preauthkeys doesn't work properly

Is this a support request?

• This is not a support request

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

Ince the re implementation in https://github.com/juanfont/headscale/commit/c9bbb5bdec1dd52ed91248a718d74acb7b52e493 the behavior of the POST /api/v1/preauthkey route doesn't work the intended way

When giving a username it doesn't work like before and returns a 400 Bad Request proto: (line 1:9): invalid value for uint64 field user: "[email protected]"

Expected Behavior

It should create and return the preauthkey

Steps To Reproduce

1. POST on /api/v1/preauthkey with a correct username for the property "user"
2. Should return an error similar to proto: (line 1:9): invalid value for uint64 field user: "[email protected]"

Environment

- OS: Ubuntu 22.04 / Docker
- Headscale version: 0.29.x (tested on .1 and .2)
- Tailscale version: (On API so not relevent for this issue)

Runtime environment

• Headscale is behind a (reverse) proxy
• Headscale runs in a container

Debug information

Running on any standard Headscale instance in 0.29.2, this is an API issue