TerraformでSecrets Managerに登録されたシークレット値をLambdaの環境変数に定義する

resource "aws_ecs_task_definition" "keycloak" {
  container_definitions = jsonencode(
    [
      {
        secrets = [
          {
            name : "KeycloakSettings__AdminUser",
            valueFrom : "${var.secrets_manager_secret_arn}: KeycloakSettings__AdminUser::"
          }
        ...
        ]
      }
    ]
  )
}

data "aws_secretsmanager_secret" "keycloak_env" {
  name = var.secrets_manager_secret_name
}

data "aws_secretsmanager_secret_version" "keycloak_env" {
  secret_id = data.aws_secretsmanager_secret.keycloak_env.id
}

data "external" "keycloak_env_secret_json" {
  program = ["echo", "${data.aws_secretsmanager_secret_version.keycloak_env.secret_string}"]
}

resource "aws_lambda_function" "keycloak" {
    environment {
    variables = {
      KeycloakSettings__AdminUser = "${data.external.keycloak_env_secret_json.result["KeycloakSettings__AdminUser"]}"
    }
  }
}