[CLI] Create whole app from OpenAPI

[kjdelisle]

Story

As a loopback4 user, I would like to use a quick command on the CLI to read in my OpenAPI spec and generate a REST API project that is the working version of that specification.

**REVISIT THIS ISSUE AFTER #739 **

Acceptance Criteria

• Read OpenAPI spec and
  • For each "server":
    • parse the basePath, protocol type (http/s) and port number
    • create a Server instance?
    • create all listed routes as controllers
    • for each controller:
      • associate the controller with the particular server instance that owns it
      • create each CRUD method for the listed operations underneath
    • for each schema in "components/schemas"
      • generate a (class/type/interface) to represent the schema
  • Add all servers to the application context

[bajtos]

Cross-posting #700 (comment) from @M-jerez:

This probably has been discussed before, but I would go the other way around, I would define the models using the Swagger/OpenAPI schema, and generate TS interface/class to extend/implement.
This would allow for much better tooling for models creation/edition without coding requirements (thinking on CRM-CMS) and still

[bajtos]

I think this feature will be done one #1399 lands.

[dhmlau]

Closing it as done.