Add GitHub Actions workflow

.github/workflows/terraform.staging.yml

@@ -0,0 +1,39 @@
+name: Terraform Staging Workflow
+on:
+  push:
+    branches:
+      - "*"
+
+concurrency:
+  group: merge-${{ github.ref }}
+
+jobs:
+  terraform:
+    runs-on: ubuntu-latest
+    environment: Staging
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - uses: 'google-github-actions/auth@v2'
+        with:
+          credentials_json: '${{ secrets.GOOGLE_CREDENTIALS }}'
+
+      - name: Set up Terraform
+        uses: hashicorp/setup-terraform@v3
+        with:
+          terraform_version: 1.8.4
+          terraform_wrapper: false
+
+      - name: Terraform Init
+        run: terraform init
+
+      - name: Terraform Workspace
+        run: terraform workspace select staging
+
+      - name: Terraform Apply
+        run: terraform apply -auto-approve
+        env:
+          TF_VAR_region: "asia-southeast1"
+          TF_VAR_environment: "staging"
+          TF_VAR_telegram_bot_token: ${{ secrets.TELEGRAM_BOT_TOKEN }}

variables.dev.tf → variables.tf

@@ -1,6 +1,5 @@
 variable "environment" {
-  type    = string
-  default = "dev"
+  type = string
 }
 
 variable "telegram_bot_token" {