Move off Trac - Execution - Forgejo

[btlogy]

Following #4095 (MoveOffTrac - Initiation), we can now start executing the plan.

In short, the goal is to follow the principle of Infrastructure as Code as much as possible in those main steps:

1. deploy and manage a new VPS server hosted by Hetzner using ​OpenToFu
2. deploy and configure Forgio using ​NixOS
3. manage the DNS records to re-route web traffic to the new server using ​OpenToFu
4. proxy/redirect out-of-scope content to the legacy server using ​NixOS
5. migrate the data from Trac to Forgejo using ​trac2gitea

More details should be found in this dedicated ​MoveOffTrac repository.

[btlogy]

Declarative definition of the DNS configurations via #4162 would be a very nice to have for the step 3 in the description.

We would be able to stream the IPs assigned to the VPS during their provisioning directly to the DNS records.

This would avoid a back-and-forth and/or synchronized interaction between the contributor(s) who's going to execute the migration and the one(s) have the permissions to change the DNS configurations.

This being said, the declarative definition of the VPS can be done regardless of what will happened to #4162. So we/I should try to keep those as separated as possible.

[btlogy]

The last step described above (5) will require access to the existing server. Brian has been sent 2 new ssh keys to be authorized to access tahoe-lafs.org...

[btlogy]

Heads up about the steps in the description:

1. Completed via ​infrastructure#21.
2. In progress via ​infrastructure#32 or ​infrastructure#33. The next PRs will be cherry picked from ​infrastructure#28
3. Pending on having access to the DNS (as discussed with Brian) via #4162
4. and 5. Pending on having access to the existing server (as discussed with Brian too)