Add support for specific container name (#17)

* Added service name output.
Introduced new optional input to specify container name explicitly,

* Added support for overriding container name in task definition

* Setting name_prefix as task id

* Removed task definition id

* Formatting

* Fixed typo

* Added variables for overriding container name

* Reintroduced container name support without explicit flag.

main.tf

@@ -111,7 +111,7 @@ resource "aws_ecs_task_definition" "task" {
 
   container_definitions = <<EOF
 [{
-    "name": "${var.name_prefix}",
+    "name": "${var.container_name != "" ? var.container_name : var.name_prefix}",
     "image": "${var.task_container_image}",
     ${local.repository_credentials_rendered}
     "essential": true,
@@ -154,7 +154,7 @@ resource "aws_ecs_service" "service" {
   }
 
   load_balancer {
-    container_name   = "${var.name_prefix}"
+    container_name   = "${var.container_name != "" ? var.container_name : var.name_prefix}"
     container_port   = "${var.task_container_port}"
     target_group_arn = "${aws_lb_target_group.task.arn}"
   }

variables.tf

@@ -5,6 +5,11 @@ variable "name_prefix" {
   description = "A prefix used for naming resources."
 }
 
+variable "container_name" {
+  description = "Optional name for the container to be used instead of name_prefix. Useful when when constructing an imagedefinitons.json file for continuous deployment using Codepipeline."
+  default     = ""
+}
+
 variable "vpc_id" {
   description = "The VPC ID."
 }