Integrate serverless-image-handler into CDK stack

[rossng]

What's [new / improved / fixed]

• Vendor in the AWS serverless-image-handler template (with minor modifications) so that it can be deployed directly as part of the CDK stack. Eliminates manual steps, including secret creation.
• Update READMEs accordingly.

Details

Upgrading

Instructions for other developers on how to upgrade their environment after pulling this new code. Please tick (i.e. put an 'x' in) the boxes for the actions that are necessary.

• [ ] Run GraphQL Codegen in the [frontend/actions service/playout service/realtime service]
• [x] Re-install NPM packages in [insert name of folder]
• [ ] Apply Hasura migrations
• [ ] Apply Hasura metadata
• [ ] Update Auth0 rules
• [x] Update environment variables
• [x] Re-deploy AWS CDK [and update AWS environment variables]

Deployment

Instructions for how to deploy these changes to production. Please tick (i.e. put an 'x' in) the boxes for the actions that are necessary.

• [ ] Apply migrations to Hasura
• [ ] Apply metadata to Hasura
• [ ] Reload enum table/values in Hasura for [table names]
• [ ] Re-deploy frontend
• [x] Re-deploy actions service
• [ ] Re-deploy playout service
• [ ] Re-deploy real-time service
• [ ] Flush real-time service state (Redis/RabbitMQ)
• [x] Update environment variables for actions service (AWS_IMAGES_CLOUDFRONT_DISTRIBUTION_NAME, AWS_IMAGES_SECRET_ACCESS_ROLE_ARN, AWS_IMAGES_SECRET_ARN)

Any other steps necessary to re-deploy?

• Tear down existing serverless-image-handler stack.
• Refresh existing URLs saved in database (we will fix this properly at a later point!)

[EdNutting]

I feel like when I created the serverless image handler stack via the AWS "deploy template" UI, there was more to configure than the stack here shows/requires? Am I misremembering?

[rossng]

A lot of that configuration was static, so we can just pre-configure it in code. Some of it was stuff like the Secrets Manager secret, which we can now auto-provision for the user.

[EdNutting]

Should we get this merged into next?