Fix evaluation with OpenTofu in nixpkgs

[Lillecarl]

Allow extra arguments to mkTerraformProvider since OpenTofus withPlugins function overrides provider-source-address to set provider registry to registry.opentofu.org rather than registry.terrraform.io.

Not sure exactly how and when it worked before. This silently ignores any extra arguments.

Fixes this eval error:

error:
       … while evaluating 'strict' to select 'drvPath' on it
         at /builtin/derivation.nix:1:552:
       … while calling the 'derivationStrict' builtin
         at /builtin/derivation.nix:1:208:
       (stack trace truncated; use '--show-trace' to show the full trace)

       error: function 'anonymous lambda' called with unexpected argument 'provider-source-address'
       at /nix/store/3qfsm6xi1p7gghms7kjfdqzffxg41d5w-source/default.nix:22:5:
           21|   mkTerraformProvider = lib.makeOverridable (
           22|     { owner
             |     ^
           23|     , repo

See https://github.com/NixOS/nixpkgs/blob/master/pkgs/by-name/op/opentofu/package.nix#L117

TODO: Support provider-source-address so this repo doesn't require you to override registry manually. (Or improve docs regarding the differenences)

[zimbatm]

@Lillecarl would the change I pushed make sense? I'd like to avoid opening the interface without bounds

[Lillecarl]

In the let block we set provider-source-address which shadows the provider-source-address from the arglist.

, provider-source-address ? null

would make more sense tbh.

Since we don't set provider-source-address on our providers the OpenTofu withPlugins override is unclear.

I think the way they implemented that in nixpkgs is a bit clumsy, i'd prefer it if they only override an arg if it already exists.

[zimbatm]

Ok let's fix this in nixpkgs then. Do you have a working example I can use?