admin: deploy and configure cert-manager to support gandi dns01 challenges
- Deploy the webhook to use the gandi's API to generate the challenges
- Adapt the cert-manager configuration to only query the public gandi DNS If not, it askes for SOA entries in the default dns (pergamon) to determine the zone to use and try to register the challenges in private zones
- Declare the staging and production let's encrypt issuers
Related to infra/sysadm-environment#4604
/cc @teams/sysadmin