HasPermissionHandler for Auth0 SPA Authorization

using Microsoft.AspNetCore.Authorization;
using System.Collections.Generic;
using System.Linq;
using System.Security.Claims;
using System.Threading.Tasks;

namespace asdf.Infrastructure
{
    public class HasPermissionHandler : AuthorizationHandler<HasAuthorizationRequirement>
    {
        private string PERMISSION_TYPE = "permissions";
        protected override Task HandleRequirementAsync(AuthorizationHandlerContext context, HasAuthorizationRequirement requirement)
        {
            // If user does not have the permission claim, get out of here
            if (!context.User.HasClaim(claim => claim.Type == PERMISSION_TYPE && claim.Issuer == requirement.issuer))
                return Task.CompletedTask;
            
            if (getPermissionsFromUserForIssuer(context.User, requirement).Any(s => s.ToString() == requirement.scope))
                context.Succeed(requirement);

            return Task.CompletedTask;
        }

        private List<string> getPermissionsFromUserForIssuer(ClaimsPrincipal user, HasAuthorizationRequirement requirement)
        {
            return user.Claims
                .Where((c => c.Type == PERMISSION_TYPE && c.Issuer == requirement.issuer))
                .Select(c => c.ToString()).ToList();
        }
    }
}