Support Lambda images

[matthewhanson]

• Update serverless to at least 2.72
• update path in API proxy
• remove magic addition of module and handler during build (put in template)

[jkeifer]

So if we want to support serverless >=3.0, we have to remove the serverlerss-pseudo-parameters plugin. The replacement on the serverless side only supports two common parameters, region and account id. For every other use, we have to convert to using Fn:Sub.

Interestingly, we can easily process strings using the same regex as the aforementioned plugin, looking for things within a string that match the pattern #{AWS::[^}]+} and replacing the # with a $. If not already inside a Fn:Sub then we can add that.

Now, the concern becomes the fact that serverless also uses ${...} for its variable interpolation, but good news: as of 2.3.0, the parser is smart enough to leave the AWS parameters alone (see https://github.com/serverless/serverless/releases/tag/v2.3.0 and serverless/serverless#8279).

In other words, we can implement our own mini version of the pseudo parameters plugin. We could also consider logging a deprecation warning with details how to get off the #{...} syntax. But for now we'll just make things work without the plugin and see how that goes.

[jkeifer]

The removal of the module/handler magic will now result in a MissingHandler exception if the module is not defined explicitly in a lambda task definition.yml. The error looks something like this:

MissingHandler: Missing module parameter in lambda definiton.yml. The handler parameter, which sets the module, is no longer defaulted. You likely need to set it to be like:

    lambda:
      handler: lambda_function.lambda_handler

Offending <lambda_type>: <lambda_name>

See https://github.com/cirrus-geo/cirrus-geo/issues/139 for additional context.

This is as it says, a problem with the handler not being defined for a lambda. The module is inferred from the handler, and is used for lambda packaging. If the handler is missing, then it needs to be added to the definition.yml.

In the case of lambdas using the new container image support, then the above is incorrect, and the problem is that the image parameter is missing.