feat: update ecr image tagging strategy to use stable for production

- Modified Terraform configuration to tag ECR images with both `latest` and `stable`.
- `Latest` is automatically applied to the dev environment for the latest version.
- `stable` is manually tagged to indicate a version that is ready for promotion to
  the production environment.

pillarbox-monitoring-terraform/20-pillarbox-monitoring-app/data_transfer_service.tf

@@ -50,7 +50,7 @@ resource "aws_ecs_task_definition" "transfer_task" {
   container_definitions = jsonencode([
     {
       name                   = "pillarbox-monitoring-transfer"
-      image                  = "${local.ecr_repository}/pillarbox-monitoring-transfer:latest"
+      image                  = "${local.ecr_repository}/pillarbox-monitoring-transfer:${local.ecr_image_tag}"
       readonlyRootFilesystem = true
 
       # Port mapping for the container

pillarbox-monitoring-terraform/20-pillarbox-monitoring-app/locals.tf

@@ -4,7 +4,7 @@ locals {
   ecs_cluster_name = "${var.application_name}-cluster"
   is_prod          = terraform.workspace == "prod"
   ecr_repository   = "${var.account_ids["prod"]}.dkr.ecr.${data.aws_region.current.name}.amazonaws.com"
-
+  ecr_image_tag    = local.is_prod ? "stable" : "latest"
 
   opensearch = {
     domain_name   = "${var.application_name}-search"
@@ -33,4 +33,4 @@ locals {
     "srg-businessowner" = "pillarbox"
     "srg-environment"   = terraform.workspace
   }
-}
+}

pillarbox-monitoring-terraform/20-pillarbox-monitoring-app/sse_broker_service.tf

@@ -275,7 +275,7 @@ resource "aws_ecs_task_definition" "dispatch_task" {
   container_definitions = jsonencode([
     {
       name                   = "pillarbox-event-dispatcher"
-      image                  = "${local.ecr_repository}/pillarbox-event-dispatcher:latest"
+      image                  = "${local.ecr_repository}/pillarbox-event-dispatcher:${local.ecr_image_tag}"
       readonlyRootFilesystem = true
 
       portMappings = [