feat(events): support SQS queues as rule targets (#2683)

Extend the Target for Event Rule to SQS Queues.

This may be needed in situations where users want to create an Event Rule and have as a target an SQS Queue.

Closes #1786.

packages/@aws-cdk/aws-events-targets/lib/index.ts

@@ -1,5 +1,6 @@
 export * from './codepipeline';
 export * from './sns';
+export * from './sqs';
 export * from './codebuild';
 export * from './lambda';
 export * from './ecs-task-properties';

packages/@aws-cdk/aws-events-targets/lib/sqs.ts

@@ -0,0 +1,73 @@
+import events = require('@aws-cdk/aws-events');
+import iam = require('@aws-cdk/aws-iam');
+import sqs = require('@aws-cdk/aws-sqs');
+
+/**
+ * Customize the SQS Queue Event Target
+ */
+export interface SqsQueueProps {
+
+  /**
+   * Message Group ID for messages sent to this queue
+   *
+   * Required for FIFO queues, leave empty for regular queues.
+   *
+   * @default - no message group ID (regular queue)
+   */
+  readonly messageGroupId?: string;
+
+  /**
+   * The message to send to the queue.
+   *
+   * Must be a valid JSON text passed to the target queue.
+   *
+   * @default the entire CloudWatch event
+   */
+  readonly message?: events.RuleTargetInput;
+
+}
+
+/**
+ * Use an SQS Queue as a target for AWS CloudWatch event rules.
+ *
+ * @example
+ *
+ *    // publish to an SQS queue every time code is committed
+ *    // to a CodeCommit repository
+ *    repository.onCommit(new targets.SqsQueue(queue));
+ *
+ */
+export class SqsQueue implements events.IRuleTarget {
+
+  constructor(public readonly queue: sqs.IQueue, private readonly props: SqsQueueProps = {}) {
+  }
+
+  /**
+   * Returns a RuleTarget that can be used to trigger this SQS queue as a
+   * result from a CloudWatch event.
+   *
+   * @see https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/resource-based-policies-cwe.html#sqs-permissions
+   */
+  public bind(rule: events.IRule): events.RuleTargetProperties {
+    // deduplicated automatically
+    this.queue.grantSendMessages(new iam.ServicePrincipal('events.amazonaws.com',
+      {
+        conditions: {
+          ArnEquals: { "aws:SourceArn": rule.ruleArn }
+        }
+      })
+    );
+
+    const result = {
+      id: this.queue.node.id,
+      arn: this.queue.queueArn,
+      input: this.props.message,
+    };
+    if (!!this.props.messageGroupId) {
+      Object.assign(result, { sqsParameters: { messageGroupId: this.props.messageGroupId } });
+    }
+    return result;
+
+  }
+
+}