scheduler/worker api: allow to use username and password to autoregister

When using username/password, ones can autoregister from any ips and admins can
retrieve worker token when registering an already existing worker.

Signed-off-by: Rémi Duraffort <remi.duraffort@linaro.org>
Status Job ID Name Coverage
  Test
passed #110453
amd64
dispatcher-debian-10

00:02:23

passed #110455
amd64
dispatcher-debian-11

00:03:01

passed #110454
amd64
server-debian-10

00:02:52

passed #110456
amd64
server-debian-11

00:05:29

 
  Analyze
passed #110457
amd64-dind
bandit-sast

00:00:50

passed #110458
amd64
black

00:00:34

passed #110459
amd64
code_quality

00:00:21

passed #110464
amd64
codespell

00:00:16

passed #110460
amd64
coverage

00:06:23

61.86%
passed #110461
amd64
dockerfiles

00:00:15

passed #110463
amd64
pylint

00:03:00

passed #110462
amd64
schemas

00:00:29

 
  Build
passed #110466
amd64
debian/10

00:01:18

passed #110465
amd64
doc

00:00:37

passed #110467
amd64-dind
docker-amd64-dispatcher

00:03:40

passed #110468
amd64-dind
docker-amd64-server

00:04:02