Add a way to have a per device documentation link

Permits to have a custom documentation link on each device.

I have one use case in mind:
A device user could want to know how to fix a device which is bad due to infra error
and so need to see documentation for this device.
19 jobs for documentation-link in 16 minutes and 28 seconds (queued for 7 seconds)
latest
Status Name Job ID Coverage
  Test
passed dispatcher-debian-10 #167958
amd64

00:02:41

passed dispatcher-debian-11 #167960
amd64

00:02:41

passed server-debian-10 #167959
amd64

00:02:51

passed server-debian-11 #167961
amd64

00:05:01

 
  Analyze
passed bandit-sast #167962
amd64-dind

00:00:56

passed black #167965
amd64

00:00:53

passed code_quality #167966
amd64

00:00:26

passed codespell #167971
amd64

00:00:22

passed coverage #167967
amd64

00:07:01

60.94%
passed dockerfiles #167968
amd64

00:00:19

passed eslint-sast #167963
amd64-dind

00:00:26

passed pylint #167970
amd64

00:02:39

passed schemas #167969
amd64

00:00:35

passed semgrep-sast #167964
amd64-dind

00:00:53

 
  Build
passed debian/10 #167973
amd64

00:01:33

passed debian/11 #167974
amd64

00:01:40

passed doc #167972
amd64

00:00:38

passed docker-amd64-dispatcher #167975
amd64-dind

00:03:49

passed docker-amd64-server #167976
amd64-dind

00:04:19