refactor: default to opentofu

Terraform has switched to an unfree license and is no longer provided by
the devShell. Thoenix now executes `tofu` by default. The command can be
specified with the `--command`, `-c` flag. Compatibility has been
otherwise maintained with this release.

crates/cli/src/commands.rs

@@ -41,4 +41,7 @@ pub(crate) struct Terraform {
     #[arg()]
     /// the arguments to pass to terraform
     pub args: Vec<String>,
+    /// the command to run when invoking terraform
+    #[arg(long, short, default_value = "tofu")]
+    pub command: String,
 }

crates/cli/src/terraform.rs

@@ -67,7 +67,7 @@ impl crate::commands::Terraform {
 
         // Call the terraform executable with the provided args
         info!(?configuration_directory, ?self.args, "invoking terraform");
-        let terraform = tokio::process::Command::new("terraform")
+        let terraform = tokio::process::Command::new(&self.command)
             .arg(format!("-chdir={}", configuration_directory.display()))
             .args(self.args)
             .spawn()?;

flake-parts/shells.nix

@@ -21,7 +21,7 @@
       # formatting
       self'.packages.treefmt
       # misc
-      pkgs.terraform
+      pkgs.opentofu
     ];
   in {
     devShells = {