nixos/nextcloud: Conditionally enable ImageMagick PHP extension

[BBBSnowball]

Motivation for this change

This adds an option that disables the ImageMagick PHP extension for NextCloud. Admins may want to do so if they don't trust ImageMagick to be secure. This fixes #115279

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[dasJ]

Huh? Why is this a disable option now instead of an enable option? I thought the de-facto standard in nixpkgs was to do enable options. This starts an annoying inconsistency here

[BBBSnowball]

The reason is in the discussion of the associated issue:

As imagemagick enabled will remain the default, I'd suggest services.nextcloud.disableImagemagick.

I have a slight preference for the enable option because it avoids thinking in double negation. However, I don't think we should do incompatible config changes without a good reason (even in unstable). Some documentation that states "please use enable" would certainly be a good reason, I think. NixOS option search finds a few disable options but not many and half of them are probably just named after what ends up in the config file (i.e. we haven't choosen that name).

In any case, I think "ImageMagick is enabled" should remain the default.

If we want it changed, I can create a PR for that.

[Ma27]

However, I don't think we should do incompatible config changes without a good reason (even in unstable).

Using mkRemovedOptionModule isn't a problem though.

In any case, I think "ImageMagick is enabled" should remain the default.

Agreed. I'd suggest to set it to true by default. Would you agree with that, @dasJ?

[dasJ]

Yes, keeping it enabled by default is a good idea. Something like mkEnableOption "some fancy description" // { default = true; } is probably what's needed here

[Ma27]

Yup, agree with that. Sorry for missing this in the first place :)

[BBBSnowball]

No problem ^^ :)
PR created.