Summary

Adds the route management layer for the API Gateway event handler. The main focus of this PR is to create the registry that will hold all the handlers registered to various routes and integrate it with the BaseRouter class added in #3972. Route validation functions were also added.

Changes

• Added a Route class for internally representing routes
• Added the RouteHandlerRegistry class, following the pattern established in the appsync-events and appsync-resolver event handlers.
  • The registry exposes a register function where handlers are registered and stored by route id (HttpMethod:path) and by HTTP method
  • Handles duplicate added routes in a last one wins fashion
  • Validates routes and logs a warning for invalid paths and skips adding them
  • Provides methods to query the registry for size, routes and routes by HTTP method
• Updated the BaseRouter class:
  • route method is no longer abstract and registration of routes using the RouteHandlerRegistry class is done in one place here
  • Removed unnecessary third argument for HTTP method functions
• Added utilities for working with paths:
  • I have chosen not add these as static methods in a class as suggested in Feature request: Implement Route Management System for Event Handler #4139. Instead, I have create a utility module with the new functions. My reasoning is that these are pure functions that do not require the incidental complexity of a class. As the experience with the EnvService has shown, should we wish to use these elsewhere in the future, it is easier to use plain functions rather than require consumers to instantiate a class with multiple methods when all they might want is one function.
  • This module defines a strict regex to define what form parameters in a path (e.g., /user/:userId) can take.
    • The first character of a parameter must be a colon
    • A parameter can only contain one colon
    • The first character after the colon must be a letter or an underscore
    • Characters after the first letter must be letters, numbers or underscores
    • Multiple parameters are permitted, e.g., /:param1/:param2/:param3
  • The validatePathPattern function ensures that parameters conform to the rules described above
  • The compilePath function is responsible for converting paths into regexes that will then be used when implementing Feature request: Implement Route Matching & Resolution System for Event Handler #4140
• Added tests for all newly added classes and updated the BaseRouter tests to reflect the changes made there.

Issue number: closes #4139

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