Kavita/API/Controllers/AdminController.cs

using System.Threading.Tasks;
using API.Data.ManualMigrations;
using API.Entities;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Mvc;

namespace API.Controllers;

#nullable enable

public class AdminController : BaseApiController
{
    private readonly UserManager<AppUser> _userManager;

    public AdminController(UserManager<AppUser> userManager)
    {
        _userManager = userManager;
    }

    /// <summary>
    /// Checks if an admin exists on the system. This is essentially a check to validate if the system has been setup.
    /// </summary>
    /// <returns></returns>
    [AllowAnonymous]
    [HttpGet("exists")]
    public async Task<ActionResult<bool>> AdminExists()
    {
        var users = await _userManager.GetUsersInRoleAsync("Admin");
        return users.Count > 0;
    }
}