Add ECR resource for publishing Secure Agent image

Image will be built and publish by the CI/CD process

terraform/ecr.tf

+# this repository is being used by
+# .gitlab-ci.yml to publish the image
+resource "aws_ecr_repository" "foo" {
+  name                 = var.ecr_repository_name
+  tags = var.ecr_repository_tags
+}
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