Feature Request: Add JWT Authorizer support to local start-api

[kstro21]

Describe your idea/feature/enhancement

When creating a Function with the following Event

      Events:
        Post:
          Type: HttpApi
          Properties:
            Path: /username
            ApiId: !Ref MyApi
            Method: POST
            Auth:
              Authorizer: OAuth2Authorizer

If we deploy and invoke the Lambda on AWS, the event will contain all of the claims of the token, for example

"requestContext": {
    "accountId": "123456789",
    "apiId": "asadsasd",
    "authorizer": {
        "jwt": {
            "claims": {
                "aud": "asdase123asdasdasd123123",
                "auth_time": "1618362653",
                "exp": "1618366253",
                "iat": "1618362653",
                "iss": "https://cognito-idp.us-east-1.amazonaws.com/us-east-1_asdasdasd",
                "sub": "73a700f4-e656-4213-937a-177c4488421c",
                "token_use": "access"
            },
            "scopes": null
        }
    },
    "domainName": "some.domain.com",
    "domainPrefix": "some",
    "http": {
        "method": "POST",
        "path": "/username",
        "protocol": "HTTP/1.1",
        "sourceIp": "1.2.3.4",
        "userAgent": "Mozilla/5.0"
    },
    "requestId": "asdasdas123123=",
    "routeKey": "POST /username",
    "stage": "myStage"
}

So, if I need to get the sub value, it is under the path at requestContext.authorizer.jwt.claims.sub.

But, locally, this is really hard to mock using sam local start-api

Proposal

When using the sam local start-api and a function has an Event with an authorizer, if the requests contain the Authorization header with a token, decode the token and update the event to match how it works on AWS by setting all of the claims under the path requestContext.authorizer.jwt.claims

Additional Details

Using SAM CLI 1.22.0

[mildaniel]

Thanks for the feature request! We have a roadmap here, but we also try to take in popular feature requests based on 👍🏽 from the community. We will be adding this to our intake for prioritization.