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 #114577
amd64
dispatcher-debian-10

00:02:34

passed #114579
amd64
dispatcher-debian-11

00:03:09

passed #114578
amd64
server-debian-10

00:03:12

passed #114580
amd64
server-debian-11

00:05:30

 
  Analyze
passed #114581
amd64-dind
bandit-sast

00:00:55

passed #114582
amd64
black

00:00:42

passed #114583
amd64
code_quality

00:00:21

passed #114588
amd64
codespell

00:00:18

passed #114584
amd64
coverage

00:06:45

60.91%
passed #114585
amd64
dockerfiles

00:00:14

passed #114587
amd64
pylint

00:03:10

passed #114586
amd64
schemas

00:00:31

 
  Build
passed #114590
amd64
debian/10

00:01:22

passed #114589
amd64
doc

00:00:36

passed #114591
amd64-dind
docker-amd64-dispatcher

00:03:37

passed #114592
amd64-dind
docker-amd64-server

00:04:02