title: how to set existing kinesis stream arn in function event
body: <p>I'm using serverless framework and trying to deploy Lambda function with event/trigger definition.
  The event source is Kinesis stream that already exist.
  I'm trying to set the stream ARN with Fn::Join function, but it seems not supported.
  How can I set the event stream ARN without hard coding the AWS region and account Id?</p>
  
  <p>My yml code:</p>
  
  <pre><code>functions:
      myfunction:
      handler: myfunction.handler
      name: myfunction-name
      memorySize: 128
      timeout: 120
      events:
        - stream:
            type: kinesis
            arn:
              Fn::Join:
                - ""
                - - "arn:aws:kinesis:"
                  - Ref: AWS::Region
                  - ":"
                  - Ref: AWS::AccountId
                  - ":stream/xxxxxxx"
            batchSize: 300
            startingPosition: LATEST
            enabled: true
  </code></pre>