Get Terraform version from dotfile in workflow

* Gets the terraform version from the dotfile and sets it as a variable
  to be used throughout the workflow. Prevents needing to update all the
  docker image references when the terraform version is updated

.github/workflows/continuous-integration-terraform.yml

@@ -13,36 +13,45 @@ jobs:
       - name: Check out code
         uses: actions/checkout@v4
 
-      - name: Check for terraform version mismatch
+      - name: Get terraform version
+        id: get-terraform-version
         run: |
           DOTFILE_VERSION=$(cat .terraform-version)
-          TERRAFORM_IMAGE_REFERENCES=$(grep "uses: docker://hashicorp/terraform" .github/workflows/continuous-integration-terraform.yml | grep -v TERRAFORM_IMAGE_REFERENCES | wc -l | tr -d ' ')
-          if [ "$(grep "docker://hashicorp/terraform:${DOTFILE_VERSION}" .github/workflows/continuous-integration-terraform.yml | wc -l | tr -d ' ')" != "$TERRAFORM_IMAGE_REFERENCES" ]
-          then
-            echo -e "\033[1;31mError: terraform version in .terraform-version file does not match docker://hashicorp/terraform versions in .github/workflows/continuous-integration-terraform.yml"
-            exit 1
-          fi
+          echo "version=$DOTFILE_VERSION" >> $GITHUB_OUTPUT
 
       - name: Remove AWS backend
         run: rm ./backend.tf
 
+      - name: Pull Terraform image
+        run: |
+          docker pull hashicorp/terraform:${{ steps.get-terraform-version.outputs.version }}
+
       - name: Run a Terraform init
-        uses: docker://hashicorp/terraform:1.5.5
-        with:
-          entrypoint: terraform
-          args: init
+        run: |
+          docker run \
+            --rm \
+            -v $(pwd):/terraform \
+            -w /terraform \
+            hashicorp/terraform:${{ steps.get-terraform-version.outputs.version }} \
+            init
 
       - name: Run a Terraform validate
-        uses: docker://hashicorp/terraform:1.5.5
-        with:
-          entrypoint: terraform
-          args: validate
+        run: |
+          docker run \
+            --rm \
+            -v $(pwd):/terraform \
+            -w /terraform \
+            hashicorp/terraform:${{ steps.get-terraform-version.outputs.version }} \
+            validate
 
-      - name: Run a Terraform format check
-        uses: docker://hashicorp/terraform:1.5.5
-        with:
-          entrypoint: terraform
-          args: fmt -check=true -diff=true
+      - name: Run a Terraform fmt
+        run: |
+          docker run \
+            --rm \
+            -v $(pwd):/terraform \
+            -w /terraform \
+            hashicorp/terraform:${{ steps.get-terraform-version.outputs.version }} \
+            fmt -check=true -diff=true
 
   terraform-docs-validation:
     name: Terraform Docs validation

variables.tf

@@ -4,7 +4,7 @@ variable "project_name" {
 }
 
 variable "aws_region" {
-  description = "AWS region in which to launch resources"
+  description      = "AWS region in which to launch resources"
   type        = string
 }