Add Role unsetting functionality

src/Imprink.Application/Users/DeleteUserRoleHandler.cs

@@ -0,0 +1,29 @@
+using Imprink.Application.Users.Dtos;
+using Imprink.Domain.Entities.Users;
+using MediatR;
+
+namespace Imprink.Application.Users;
+
+public record DeleteUserRoleCommand(string Sub, Guid RoleId) : IRequest<UserRoleDto?>;
+
+public class DeleteUserRoleHandler(IUnitOfWork uw) : IRequestHandler<DeleteUserRoleCommand, UserRoleDto?>
+{
+    public async Task<UserRoleDto?> Handle(DeleteUserRoleCommand request, CancellationToken cancellationToken)
+    {
+        if (!await uw.UserRepository.UserExistsAsync(request.Sub, cancellationToken)) return null;
+
+        var userRole = new UserRole
+        {
+            UserId = request.Sub,
+            RoleId = request.RoleId
+        };
+        
+        var removedRole = await uw.UserRoleRepository.RemoveUserRoleAsync(userRole, cancellationToken);
+
+        return new UserRoleDto
+        {
+            UserId = removedRole.UserId,
+            RoleId = removedRole.RoleId
+        };
+    }
+}