重构项目结构，移除Assignment相关功能，优化Submission模块

TechHelper.Server/Services/Class/IClassService.cs

@@ -0,0 +1,16 @@
+using Entities.DTO;
+using Entities.DTO.Class;
+using SharedDATA.Api;
+
+namespace TechHelper.Services.Beta
+{
+    public interface IClassService : IBaseService<ClassDto, Guid>
+    {
+        Task<ApiResponse> GetClassStudentsAsync(Guid classId);
+        Task<ApiResponse> UserRegister(RegisterUserToClassDto user);
+        Task<ApiResponse> ValidateClassRegistration(ClassValidDto user);
+        Task<ApiResponse> GetUserInjoinedClasses(Guid user);
+		Task<ApiResponse> GetUserClassRole(Guid id);
+		Task<ApiResponse> AdminAddAsync(ClassCreateDto dto);
+	}
+}