feat: support built-in JavaScript/Node schema types

[hacksparrow]

Adds support for Date type and includes test for pre-existing types.

For fixing: #1112

A new issue has been created for items under "nice to have" - #1742.

Checklist

• npm test passes on your machine
• New tests added or existing tests modified to cover all changes
• Code conforms with the style guide
• API Documentation in code was updated
• Documentation in /docs/site was updated
• Affected artifact templates in packages/cli were updated
• Affected example projects in examples/* were updated

[bajtos]

I think JavaScript Date should be described as date-time, because Date holds both date and time.

https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.1.md#data-types

Common Name	type	format	Comments
date	string	date	As defined by full-date - RFC3339
dateTime	string	date-time	As defined by date-time - RFC3339

LoopBack 3.x describes Date properties as {type: 'string', format: 'date-time'} too, see loopback-swagger's lib/specgen/schema-builder.js:

    case 'date':
      schema.type = 'string';
      schema.format = 'date-time';
      break;

[hacksparrow]

@bajtos made the changes.

[bajtos]

type: 'string', 
format: 'date-time',

[bajtos]

@hacksparrow before you fix this: please look around the tests and try to find a test that runs JSON Schema validation against the JSON/OpenAPI schema we are producing.

Ideally, if our schema builder emits an invalid schema (as you did here), then there should be a test that fails and reports the problem.

[bajtos]

Maybe we have an acceptance test that needs to be expanded with the newly supported types?

[hacksparrow]

Noted.

[hacksparrow]

@bajtos made the changes you suggested.

[bajtos]

Nice 👍

Please clean up the git history before merging.

[raymondfeng]

Please fix the lint issue before merging - https://travis-ci.org/strongloop/loopback-next/jobs/431549108