Document new lifecycle hooks for dispatcher and scheduler

And reduce a bit the implementation.

README.md

@@ -375,9 +375,9 @@ In Solid queue, you can hook into two different points in the supervisor's life:
 - `start`: after the supervisor has finished booting and right before it forks workers and dispatchers.
 - `stop`: after receiving a signal (`TERM`, `INT` or `QUIT`) and right before starting graceful or immediate shutdown.
 
-And into two different points in a worker's life:
-- `worker_start`: after the worker has finished booting and right before it starts the polling loop.
-- `worker_stop`: after receiving a signal (`TERM`, `INT` or `QUIT`) and right before starting graceful or immediate shutdown (which is just `exit!`).
+And into two different points in the worker's, dispatcher's and scheduler's life:
+- `(worker|dispatcher|scheduler)_start`: after the worker/dispatcher/scheduler has finished booting and right before it starts the polling loop or loading the recurring schedule.
+- `(worker|dispatcher|scheduler)_stop`: after receiving a signal (`TERM`, `INT` or `QUIT`) and right before starting graceful or immediate shutdown (which is just `exit!`).
 
 You can use the following methods with a block to do this:
 ```ruby
@@ -386,6 +386,12 @@ SolidQueue.on_stop
 
 SolidQueue.on_worker_start
 SolidQueue.on_worker_stop
+
+SolidQueue.on_dispatcher_start
+SolidQueue.on_dispatcher_stop
+
+SolidQueue.on_scheduler_start
+SolidQueue.on_scheduler_stop
 ```
 
 For example:

lib/solid_queue.rb

@@ -43,28 +43,14 @@ module SolidQueue
 
   delegate :on_start, :on_stop, to: Supervisor
 
-  def on_worker_start(...)
-    Worker.on_start(...)
-  end
-
-  def on_worker_stop(...)
-    Worker.on_stop(...)
-  end
-
-  def on_dispatcher_start(...)
-    Dispatcher.on_start(...)
-  end
-
-  def on_dispatcher_stop(...)
-    Dispatcher.on_stop(...)
-  end
-
-  def on_scheduler_start(...)
-    Scheduler.on_start(...)
-  end
-
-  def on_scheduler_stop(...)
-    Scheduler.on_stop(...)
+  # on_worker_start, on_worker_stop, on_dispatcher_start ...
+  %w[ worker dispatcher scheduler ].each do |process|
+    %w[ start stop ].each do |action|
+      define_method("on_#{process}_#{action}") do |&block|
+        # Worker.on_start(&block), Dispatcher.on_stop(&block)
+        const_get(process.capitalize).public_send("on_#{action}", &block)
+      end
+    end
   end
 
   def supervisor?