Router - Return 503 if Lambda Invoke gives permission error

[huntharo]

Motivations

• Currently, if the Lambda Invoke gets a permission error, it will just keep retrying until it times out the request
• Need to add a test to make sure that this case ends (stops trying to invoke and removes the request as in progress)
• Should return a 503 immediately to the caller when the error is: is not authorized to perform: lambda:InvokeFunction on resource:
  • There is no direct relationship between the PendingRequests and the Lambdas 
  • Perhaps when the LIM detects this error it should notify the Dispatcher to clear all pending requests with a 503

Acceptance Criteria

• [ ] Add LambdaInstanceManager test that simulates lambda invoke giving a 503
• [ ] Raise event from LIM when Lambda gives a 503
• [ ] Subscribe to event in Dispatcher - Clear all pending requests when a 503 is received
• [ ] Add Dispatcher test for the event clearing the pending requests