Add foreign key relationship to RecAction class

Enhanced the `RecAction` class by adding a navigation property
(`Endpoint`) to represent the relationship with the `Endpoint`
entity. Annotated the `Endpoint` property with the
`[ForeignKey("EndpointId")]` attribute to establish the foreign
key mapping. This improves the data model by explicitly defining
the relationship between `RecAction` and `Endpoint`.

src/ReC.Domain/Entities/RecAction.cs

@@ -25,6 +25,9 @@ public class RecAction
     [Column("ENDPOINT_ID")]
     public long? EndpointId { get; set; }
 
+    [ForeignKey("EndpointId")]
+    public Endpoint? Endpoint { get; set; }
+
     [Column("ENDPOINT_AUTH_ID")]
     public long? EndpointAuthId { get; set; }