Help users debug API Gateway timeout (29 seconds)

[deliahu]

Description

Requests return 503 without including any info in the request body or cortex logs. It would be good to mention in one or both of these placed that this is a timeout. We could also consider mentioning that the user might not want to use API gateway, but that could be undesirable in a production environment (it would only be helpful in dev).

Relevant info

A solution could be in using an integration response for timeouts with lambdas:

• https://stackoverflow.com/a/31371862/2096747
• https://docs.aws.amazon.com/sdk-for-go/api/service/apigatewayv2/#ApiGatewayV2.CreateIntegrationResponse

[miguelvr]

closed #1751