Allow abstract classes to be used as identifiers

[remojansen]

Extending ServiceIdentifier<T> to accept Abstract classes.

Constructor of abstract class can be used as service identifier and can also be binded to a concret implementation.

// Declare interface as below
@injectable()
abstract class MyServiceInterface { void f(); }

class MyService extends MyServiceInterface { /*...*/ }

// Inject as below
class MyBusiness {
  constructor(@inject(MyServiceInterface) x: MyServiceInterface) {
    /*...*/
  }
}

And such way should be more easier than injecting an interface, which need to define a symbol for it.

This was reported by https://github.com/inversify/inversify-dts/pull/19

[remojansen]

Done by 38b9a8a

[mpontus]

Does this eliminate the need to maintain TYPES object if every interface was replaced with an abstract class? Are there any downsides to using this approach?

[Exifers]

I was looking for an IOC container for Typescript that allows usage of abstract classes like this.

Unless I haven't seen it it's not specified in the npm doc that abstract classes can be used as identifiers.
Maybe this could be worth mentioning it, as it simplifies a lot compared to maintaining TYPES.