Merge pull request #1420 from getspooky/my-providers-branch

feat(content/fundamentals): Use TypeScript Enums as token values

Author: kamilmysliwiec

content/fundamentals/dependency-injection.md

@@ -185,7 +185,7 @@ export class AppModule {}
 
 In this example, we are associating a string-valued token (`'CONNECTION'`) with a pre-existing `connection` object we've imported from an external file.
 
-> warning **Notice** In addition to using strings as token values, you can also use JavaScript [symbols](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol).
+> warning **Notice** In addition to using strings as token values, you can also use JavaScript [symbols](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol) or TypeScript [enums](https://www.typescriptlang.org/docs/handbook/enums.html).
 
 We've previously seen how to inject a provider using the standard [constructor based injection](https://docs.nestjs.com/providers#dependency-injection) pattern. This pattern **requires** that the dependency be declared with a class name. The `'CONNECTION'` custom provider uses a string-valued token. Let's see how to inject such a provider. To do so, we use the `@Inject()` decorator. This decorator takes a single argument - the token.