Add Terraform documentation and example variable files

Co-authored-by: sayedimac <25403967+sayedimac@users.noreply.github.com>

Author: Copilot

azd/TERRAFORM.md

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+# Terraform Infrastructure
+
+This directory contains Terraform configurations that are equivalent to the Bicep templates in this repository. You can choose to use either Bicep or Terraform for deploying the infrastructure.
+
+## Structure
+
+Each deployment option has its own directory with Terraform configurations:
+
+- **aca/** - Azure Container Apps deployment
+- **aci/** - Azure Container Instance deployment
+- **aks/** - Azure Kubernetes Service deployment
+- **acr/** - Standalone Azure Container Registry module
+
+## Prerequisites
+
+1. [Terraform](https://www.terraform.io/downloads) >= 1.0
+2. [Azure CLI](https://docs.microsoft.com/en-us/cli/azure/install-azure-cli)
+3. An active Azure subscription
+
+## Authentication
+
+Before running Terraform, authenticate with Azure:
+
+```bash
+az login
+```
+
+## Usage
+
+### Azure Container Apps (ACA)
+
+```bash
+cd azd/aca
+
+# Initialize Terraform
+terraform init
+
+# Review the execution plan
+terraform plan -var="environment_name=myenv" -var="location=eastus"
+
+# Apply the configuration
+terraform apply -var="environment_name=myenv" -var="location=eastus"
+```
+
+### Azure Container Instance (ACI)
+
+```bash
+cd azd/aci
+
+# Initialize Terraform
+terraform init
+
+# Review the execution plan
+terraform plan -var="environment_name=myenv" -var="location=eastus"
+
+# Apply the configuration
+terraform apply -var="environment_name=myenv" -var="location=eastus"
+```
+
+### Azure Kubernetes Service (AKS)
+
+```bash
+cd azd/aks
+
+# Initialize Terraform
+terraform init
+
+# Review the execution plan
+terraform plan -var="environment_name=myenv" -var="location=eastus"
+
+# Apply the configuration
+terraform apply -var="environment_name=myenv" -var="location=eastus"
+```
+
+## Variables
+
+Each deployment option has configurable variables. Here are the common ones:
+
+### Required Variables
+
+- `environment_name` - Name of the environment (1-64 characters)
+- `location` - Azure region (e.g., "eastus", "westus2")
+
+### Optional Variables (ACA)
+
+- `container_image` - Container image to deploy (default: "docker-app")
+- `container_port` - Port the container listens on (default: 80)
+- `cpu_cores` - CPU cores allocated (default: "0.5")
+- `memory_in_gb` - Memory allocated (default: "1Gi")
+
+### Optional Variables (ACI)
+
+- `container_image` - Container image to deploy (default: "mcr.microsoft.com/azuredocs/aci-helloworld")
+- `container_port` - Port the container listens on (default: 80)
+- `cpu_cores` - CPU cores allocated (default: "1.0")
+- `memory_in_gb` - Memory in GB (default: "1.5")
+
+### Optional Variables (AKS)
+
+- `agent_count` - Number of agent nodes (default: 3, range: 1-100)
+- `agent_vm_size` - VM size for nodes (default: "Standard_D2s_v3")
+- `os_disk_size_gb` - OS disk size in GB (default: 0, range: 0-1023)
+- `os_type` - Operating system type (default: "Linux", options: "Linux", "Windows")
+
+## Using Variable Files
+
+You can create a `terraform.tfvars` file to store your variables:
+
+```hcl
+environment_name = "myenv"
+location         = "eastus"
+container_image  = "myregistry.azurecr.io/myapp"
+container_port   = 8080
+```
+
+Then run:
+
+```bash
+terraform apply
+```
+
+## Outputs
+
+Each configuration provides outputs that can be used for further automation:
+
+- `AZURE_LOCATION` - The Azure region where resources are deployed
+- `AZURE_CONTAINER_REGISTRY_ENDPOINT` - Container registry login server
+- `AZURE_CONTAINER_REGISTRY_NAME` - Container registry name
+- Additional outputs specific to each deployment type
+
+## Comparison with Bicep
+
+| Feature | Bicep | Terraform |
+|---------|-------|-----------|
+| Language | ARM Template DSL | HCL (HashiCorp Configuration Language) |
+| Provider | Azure-specific | Multi-cloud (Azure, AWS, GCP, etc.) |
+| State Management | Server-side (Azure) | Client-side (local or remote backend) |
+| Module System | Bicep modules | Terraform modules |
+| Validation | `az bicep build` | `terraform validate` |
+| Preview Changes | `az deployment what-if` | `terraform plan` |
+| Apply Changes | `az deployment create` | `terraform apply` |
+
+## Clean Up
+
+To destroy all resources created by Terraform:
+
+```bash
+terraform destroy -var="environment_name=myenv" -var="location=eastus"
+```
+
+Or if using a tfvars file:
+
+```bash
+terraform destroy
+```
+
+## Notes
+
+- The Terraform configurations are functionally equivalent to their Bicep counterparts
+- Both Bicep and Terraform files are maintained in this repository for flexibility
+- The `.terraform/` directory and state files are git-ignored for security
+- Always review the `terraform plan` output before applying changes

azd/aca/terraform.tfvars.example

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+# Example Terraform variables for Azure Container Apps deployment
+# Copy this file to terraform.tfvars and customize the values
+
+environment_name = "dev"
+location         = "eastus"
+
+# Optional: Container configuration
+# container_image  = "docker-app"
+# container_port   = 80
+# cpu_cores        = "0.5"
+# memory_in_gb     = "1Gi"

azd/aci/terraform.tfvars.example

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+# Example Terraform variables for Azure Container Instance deployment
+# Copy this file to terraform.tfvars and customize the values
+
+environment_name = "dev"
+location         = "eastus"
+
+# Optional: Container configuration
+# container_image  = "mcr.microsoft.com/azuredocs/aci-helloworld"
+# container_port   = 80
+# cpu_cores        = "1.0"
+# memory_in_gb     = "1.5"

azd/aks/terraform.tfvars.example

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+# Example Terraform variables for Azure Kubernetes Service deployment
+# Copy this file to terraform.tfvars and customize the values
+
+environment_name = "dev"
+location         = "eastus"
+
+# Optional: AKS configuration
+# agent_count      = 3
+# agent_vm_size    = "Standard_D2s_v3"
+# os_disk_size_gb  = 0
+# os_type          = "Linux"