Added scheduler docs

docs/_sidebar.md

@@ -8,6 +8,7 @@
     - [Middlewares](middleware.md)
     - [Interceptors](interceptor.md)
     - [Exceptions](exceptions.md)
+    - [Schedulers](schedulers.md)
 - Flutter
     - [Dartness with Flutter](flutter.md)
 

docs/schedulers.md

@@ -0,0 +1,83 @@
+# Schedulers
+
+Schedulers enables you to set arbitrary code (methods/functions) to run at a specific date and time, at regular intervals, or once after a certain duration. In the Linux environment, this is typically managed by packages such as cron at the operating system level. For Node.js applications, various packages offer cron-like functionality. Dartness offers the `@Scheduler` annotation, which works with the cron package https://pub.dev/packages/cron. This chapter will discuss this scheduling in detail.
+
+## Declarative cron jobs
+
+A cron job automatically schedules an arbitrary function (method call) to run. Cron jobs can be configured to:
+
+1. Run once at a specified date and time.
+2. Run on a recurring basis, at specified intervals (for example, once per hour, once per week, once every 5 minutes).
+
+To declare a cron job, use the @Cron() decorator before the method definition containing the code to be executed, as shown below:
+
+```dart
+import 'package:dartness_server/schedule.dart';
+
+part 'example_scheduler.g.dart';
+
+@Scheduler()
+class ExampleScheduler {
+  @Scheduled(cron: "* * * * *")
+  void example() {
+    print("${DateTime.now()} Hello world");
+  }
+}
+```
+
+In this example, the method `example()` will be called every second. As you can see, the class is annotated with `@Scheduler` to indicate that the class contains scheduler tasks and every method that needs to be scheduled is annotated with `@Scheduled` accepting as a param a cron.
+
+Now that we have a service class to retrieve cities, let's use it inside the `CityController`:
+
+```dart
+@Controller('cities')
+class CityController {
+  final CityService _cityService;
+
+  CityController(this._cityService);
+
+  @Post()
+  void create(@Body() City city) {
+    _cityService.create(city);
+  }
+
+  @Get()
+  List<City> findAll() {
+    return _cityService.findAll();
+  }
+}
+```
+
+The `CityService` is injected through the class constructor.
+
+# Provider registration
+
+Now that we have defined a provider (`CityService`), and we have a consumer of that service (`CityController`), we
+need to
+register the service with Dartness so that it can perform the injection. We do this by editing our module file (
+app.dart) and adding the service to the `providers` attribute of the `@Application()` annotation using
+the `ModuleMetadata` class in order to structure the metadata and the  `ProviderMetadata` class to structure our
+provider.
+
+```dart
+@Application(
+  module: Module(
+    metadata: ModuleMetadata(
+      controllers: [
+        ProviderMetadata(
+          classType: CityController,
+        ),
+      ],
+      providers: [
+        ProviderMetadata(
+          classType: CityService,
+        ),
+      ],
+    ),
+  ),
+)
+class App {}
+```
+
+Dartness will now be able to resolve the dependencies of the `CityController` class.
+