feat(lang): Add module for terraform-mode package

And enable formatting terraform files with `terraform fmt` through the
use of reformatter.

core/siren-core-modules.el

@@ -169,6 +169,7 @@
 (require 'siren-sh)
 (require 'siren-slim)
 (require 'siren-sql)
+(require 'siren-terraform)
 (require 'siren-text-mode)
 (require 'siren-thrift)
 (require 'siren-toml)

modules/languages/siren-terraform.el

@@ -0,0 +1,36 @@
+;;; siren-terraform.el --- jimeh's Emacs Siren: terraform-mode configuration.
+
+;;; Commentary:
+
+;; Basic configuration for terraform-mode.
+
+;;; Code:
+
+(require 'siren-reformatter)
+
+(use-package terraform-mode
+  :hook
+  (terraform-mode . siren-terraform-mode-setup)
+
+  :custom
+  (terraform-indent-level 2)
+
+  :init
+  (defun siren-terraform-mode-setup ()
+    (setq tab-width 2)
+    (format-all-mode -1)
+    (terraform-format-on-save-mode 1))
+
+  :config
+  (reformatter-define terraform-format
+    :program "terraform"
+    :args '("fmt" "-no-color" "-")
+    :lighter " TF"))
+
+(use-package company-terraform
+  :init
+  (with-eval-after-load 'terraform-mode
+    (company-terraform-init)))
+
+(provide 'siren-terraform)
+;;; siren-terraform.el ends here