fix(rest): set statusCode as 201 for POST request

[virkt25]

temporary fix for #788

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

[raymondfeng]

This is too hacky. Not all POST is for create. Can we allow/infer the statusCode from https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#responses-object?

[raymondfeng]

There are a few potential options for controller methods to express status code:

1. Direct access to Response object
2. Decorate the method to customize the default status code
3. Return a HttpResponse object such as {statusCode: 201, headers: {}, body: result}. It's similar as https://docs.oracle.com/javaee/6/api/javax/ws/rs/core/Response.ResponseBuilder.html

[virkt25]

We have issues to track the stories of providing a way for users to set the statusCode and appropriate response headers.

I personally like option 3 -- but for a POST request I think we should automatically be defaulting to 201 if a different statusCode is not provided.

[jannyHou]

@virkt25 After I did my PoC in #1260, I tend to agree with your workaround here as the quickest fix....or allowing more time, we can do proposal#3.

Miroslav brings an important thing: when a response returns 201, it also includes a header with the URI of created item.

but for a POST request I think we should automatically be defaulting to 201 if a different statusCode is not provided.

I still feel 200 is better, since if default POST to 201, the user need to provide header in result by default as well.

[virkt25]

I believe @jannyHou is investigating a less "hacky" approach so I'll close this PR for now.