chore: instruct terraform to not suggest next steps as it's running on CI

See for details:
- https://developer.hashicorp.com/terraform/tutorials/automation/automate-terraform#controlling-terraform-output-in-automation
- https://developer.hashicorp.com/terraform/cli/config/environment-variables#tf_in_automation

[skip ci]

Author: php-coder

.github/workflows/provision-by-terraform.yml

@@ -90,10 +90,16 @@ jobs:
 
       - name: Run terraform init
         working-directory: infra/terraform
+        env:
+          # https://developer.hashicorp.com/terraform/cli/config/environment-variables#tf_in_automation
+          TF_IN_AUTOMATION: true
         run: terraform init
 
       - name: Run terraform plan
         working-directory: infra/terraform
+        env:
+          # https://developer.hashicorp.com/terraform/cli/config/environment-variables#tf_in_automation
+          TF_IN_AUTOMATION: true
         run: >-
           terraform plan \
             -detailed-exitcode \