Add CreateAction POST endpoint to ActionController

A new HTTP POST endpoint `CreateAction` was added to the
`ActionController` class. This endpoint accepts a
`CreateRecActionCommand` object from the request body, sends
it to the `mediator` for processing, and returns a `201 Created`
response using the `CreatedAtAction` method. This change
enables the creation of actions via HTTP POST requests,
enhancing the controller's functionality.

src/ReC.API/Controllers/ActionController.cs

@@ -15,6 +15,7 @@ public class ActionController(IMediator mediator) : ControllerBase
         return Accepted();
     }
 
+    [HttpPost]
     public async Task<IActionResult> CreateAction([FromBody] CreateRecActionCommand command)
     {
         await mediator.Send(command);