How can we configure injectors with providers at different levels?

[akhils-nair-b6a2a78b (Akhil S Nair)]

The users can configure injectors with providers at different levels of their application by setting a metadata value. The configuration can happen in one of three places,

1. In the @Injectable() decorator for the service itself
2. In the @NgModule() decorator for an NgModule
3. In the @Component() decorator for a component