[http-server-javascript] Implement basic project scaffolding.

[witemple-msft]

Adds a new scaffolding command for http-server-js. To run it, a customer calls npx hsj-scaffold. It is opinionated, but uses some settings from tspconfig.yaml.

• Generates a server entrypoint using either express or Node depending on whether tspconfig.yaml has express: true in the emitter options.
• Generates a controller for each interface as a class that implements the business logic interface. For now, these controller methods simply throw 501 Not Implemented.
• Creates a suitable tsconfig.json to compile the project.
• Modifies package.json with scripts to build and start the server.
• Adds vscode tasks/launch configurations for debugging.

Some changes to the generator itself were required:

• Added a new helper module, helpers/http, that defines an HttpResponder as an object containing a function that can respond to an HTTP request. If the business logic implementations throw an object that is an HttpResponder, then it will be used to respond to the request instead of the default onInternalError handler. This makes it easy for any route controller handler to construct and reply with any error they like without having to satisfy the type checker.

[azure-sdk]

All changed packages have been documented.

• ✅ @typespec/http-server-javascript

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@typespec/http-server-javascript - feature ✏️

Implement basic project scaffolding.

[azure-sdk]

You can try these changes here

🛝 Playground	🌐 Website	📚 Next docs	🛝 VSCode Extension

[allenjzhang]

Please fix npm install as discussed.

[witemple-msft]

@allenjzhang The npm install issue on windows should be fixed by using shell: true when the platform is win32 (this is an annoying, evergreen Node programming bug that I always hit -- spawn and execFile cannot execute batch scripts, which npm is on windows).

@markcowl I'm going to resolve the comments per our discussion. There's more work to be done here around scaffolding hooks and proper use of the compiler APIs.