Return type narrowing for service multi CRUD.

[deskoh]

This PR narrow the return type of service multi create, patch and remove methods.

Consider the following database service:

type Message = { text: string }

// Return type: Promise<Message>
service.create({ text: 'msg' });
// Return type: Promise<Message[]>
service.create([{ text: 'msg' }]);

// Return type: Promise<Message>
service.update(1, { text: 'msg' });
// Typing error remains (Database adapter does not support multi update)
service.update(null, { text: 'msg' });

// Return type: Promise<Message>
service.patch(1, { text: 'msg' });
// Return type: Promise<Message[]>
service.patch(null, { text: 'msg' });

[pdfowler]

@deskoh I found this PR after fighting with this problem myself for a bit. What did you end up doing to resolve this issue for yourself?

[deskoh]

Take a look at this: https://github.com/feathersjs-ecosystem/databases/pull/4
The packages have been moved back in upcoming version:
https://github.com/feathersjs/feathers/blob/dove/packages/adapter-commons/src/service.ts

Seems like the overloads were removed. Any comments @vonagam?

[daffl]

Good point, they should be added back in that file now. No idea yet if it will all play together nicely, there's a lot of changes in progress at https://github.com/feathersjs/feathers/tree/dove-typescript-refactor.