Feature Request: Usage plans for Websockets API

This is a Feature Proposal

Description

AWS supports setting ApiKeyRequired to true for the $connect route. This is useful specifically when setting the apiKeySource value to "AUTHORIZER". Currently, there is no way to add these values from serverless.

My main goal is to connect the WebSockets API Gateway to the same usage plans created for the Rest API and set the ApiKeyRequired value on the $connect route which uses a custom authorizer that will provide the key because browsers don't support setting custom headers.

A possible implementation of setting the ApiKeyRequired value could look as follows.

events:
  - websocket:
      private: true
      routeKey: $connect

A possible implementation of connecting the usage plan could look as follows.

websocketsApiUsagePlans:
  - free
 usagePlan: 
   - free
     quota:
       limit: 5000
       offset: 2
       period: MONTH
     throttle:
       burstLimit: 200
       rateLimit: 100

Similar or dependent issues:

• Issue in old serverless-websocket-plugin

Start by tracing the websocket event configuration and the API Gateway usage-plan settings described in the proposal. Determine how the $connect route, ApiKeyRequired, apiKeySource, shared REST API usage plans, quotas, and throttles should be represented. Done means users can configure these values in serverless.yml and the generated AWS configuration connects the WebSockets API to the requested usage plan.