oidc username/email to create new namespace mapping is broken

[kyhwana]

Bug description
When authing a new user via oidc (with email stripping DISABLED, I didn't test with it enabled) the following error occures and the namespace isn't created:

[GIN] 2022/02/27 - 21:54:06 | 302 |     118.701µs | redacated  | GET      "/oidc/register/mkey:redacated"
2022-02-27T21:54:06Z ERR ../home/runner/work/headscale/headscale/oidc.go:319 > could not find or create namespace error="Namespace not found" namespace=redacatednamespace
[GIN] 2022/02/27 - 21:54:06 | 500 |  161.557551ms |  redacated | GET      "/oidc/callback?code=0redacated"
2022-02-27T21:54:09Z WRN Ignoring request, cannot find machine with key mkey:redacated handler=PollNetMap
[GIN] 2022/02/27 - 21:54:09 | 401 |    1.083608ms |   118.92.104.24 | POST     "/machine/redacated/map"

To Reproduce

With email stripping disabled, configure an oidc (tested with azure ad) and have a user attempt to login with [email protected].

Context info

• 0.15-beta1
• tailscale client 1.22.0
• Client OS Windows 11

[GIN] 2022/02/27 - 21:54:06 | 302 |     118.701µs | redacated  | GET      "/oidc/register/mkey:redacated"
2022-02-27T21:54:06Z ERR ../home/runner/work/headscale/headscale/oidc.go:319 > could not find or create namespace error="Namespace not found" namespace=redacatednamespace
[GIN] 2022/02/27 - 21:54:06 | 500 |  161.557551ms |  redacated | GET      "/oidc/callback?code=0redacated"
2022-02-27T21:54:09Z WRN Ignoring request, cannot find machine with key mkey:redacated handler=PollNetMap
[GIN] 2022/02/27 - 21:54:09 | 401 |    1.083608ms |   118.92.104.24 | POST     "/machine/redacated/map"

I fixed and tested this with the following fix:
Line 302 of oidc.go changed from if errors.Is(err, gorm.ErrRecordNotFound) { to if errors.Is(err, errNamespaceNotFound) {
I also had to comment out line 20 of oidc.go "gorm.io/gorm" because the go compiler complained that gorm wasn't being used :)

It looks like getnamespace returns "errNamespaceNotFound" ("Namespace not found") but the if statement on line 302 is just looking for gorm.ErrRecordNotFound and so it falls through to line 317 } else if err != nil { and errors out.