MICRO-196: Slack Alerts

[AdamJHall]

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Description of the proposed changes
This PR Adds the notificationArn prop to the GraphQL Mesh construct. Whenever this prop is provided with a valid SNS topic ARN it will forward all SNS notifications it receives for codepipeline executions to that topic.

Other solutions considered (if any)
Initially I was planning on using Codestar notification rules to send to an SNS topic and then subscribe AWS Chatbot to that SNS topic. However AWS Chatbot requires you then request access to slack for each AWS account and it grants itself access to ALL public channels. So anyone with access to AWS would then be able to see the entire Aligent channel list.

After that I attempted to setup the SNS topic in the Aligent AWS account and then just send the notification from the client account to our Aligent account. While most of the docs seem to imply this is possible, you end up just getting Invalid Request in cloudformation. I attempted to set it up manually via the CLI just to test and got the real error message of “SNS topic must be in the same account as the notification rule“.

Next attempt was to have Chatbot subscribe to an SNS topic in the client account, but that doesn’t work either as Chatbot can only subscribe to topics in it’s own account.

So AWS didn’t seem to like me just piping cloudwatch events to the SNS topic so I’m having to setup a notification rule as well.

So we end up with Notification Rule → SNS → Lambda → SNS → Chatbot.

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