feat: basic organization endpoint

WebApp/DTOs/OrganisationSummaryDto.cs

@@ -0,0 +1,11 @@
+using System.ComponentModel.DataAnnotations;
+using WebApp.Entities;
+
+namespace WebApp.DTOs;
+public record class OrganisationSummaryDto
+(
+    [Required] int? OrganisationId,
+    [Required][StringLength(50)] string Name,
+    [StringLength(500)] string Description,
+    [Required][StringLength(200)] string Website
+);