feat: return organisationId if user is an organization

this will help to determine if an event is created by the user or not

WebApp/Endpoints/AuthEndpoints.cs

@@ -71,7 +71,10 @@ namespace WebApp.Endpoints
                     return Results.Json(new {message = "No user found."}, statusCode: 404);
                 }
 
+                Organisation? org = await guh.GetOrganisationFromUserId(user.UserId);
+                if (org is not null) return Results.Ok(user.ToUserSummaryWithOrgIdDto(org.OrganisationId));
                 return Results.Ok(user.ToUserSummaryDto());
+
             })
                 .WithName(GetUserEndpointName);