Feature Request: Add Support for Additional Lambda Permissions (ex S3, SNS, etc)

[coleduclos]

• High level summary / overview of the feature request
  As a user of the Lambda plugin, I would like to create functions that can be triggered by asynchronous invocations (S3, SNS, etc).

• Details of the environment.

  • What is the version of the plugin?
    1.0.8
  • What is the version of spinnaker?
    1.26

• Current behavior
  Currently there is no way to add permissions to a Lambda that would allow it to be triggered by things like S3 buckets, SNS topics, CloudWatch events, etc. These are considered asynchronous invocations.

• Expected behavior (Detailed description of the expected behavior and how it is different from the current behavior).
  I expect there would be a way to specify permissions to be added to the Lambda function that would allow certain AWS services and specific resources to trigger the function.

Please see screenshots of this ability in the AWS console below: