nixos/signald: automatically migrate db

[Flakebi]

Description of changes

Run --migrate-data on every start, so that the database migrations don’t need to be run manually.
I’ve been running this on my server for a while.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.11 Release Notes (or backporting 22.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[Flakebi]

Ups, didn’t want to delete the branch

[onny]

Thank you for this idea :) Is this safe to use? Why doesn't signald does this by itself?

[Flakebi]

Is this safe to use?

Yes.

Why doesn't signald does this by itself?

No idea. It should be quite easy to run migrations in code but for a reason I don’t understand, some applications don’t do this.