JWT token authorization on the c# server side not clear

I have a github project link where the client sends Authorization header to the server containing the JWT token like below. What I can't understand is how on the server side [Authorize(Role.Admin)]can understand the Role.Admin which is application specific enum value (belonging to the account object - details beow).

intercept(request: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
        // add auth header with jwt if account is logged in and request is to the api url
        const account = this.accountService.accountValue;
        const isLoggedIn = account && account.jwtToken;
        const isApiUrl = request.url.startsWith(environment.apiUrl);
        if (isLoggedIn && isApiUrl) {
            request = request.clone({
                setHeaders: { Authorization: `Bearer ${account.jwtToken}` }
            });
        }

        return next.handle(request);
    }

On the server side I have middleware class containing the code that decripts the token like this:

try
            {
                var tokenHandler = new JwtSecurityTokenHandler();
                var key = Encoding.ASCII.GetBytes(_appSettings.Secret);
                tokenHandler.ValidateToken(token, new TokenValidationParameters
                {
                    ValidateIssuerSigningKey = true,
                    IssuerSigningKey = new SymmetricSecurityKey(key),
                    ValidateIssuer = false,
                    ValidateAudience = false,
                    // set clockskew to zero so tokens expire exactly at token expiration time (instead of 5 minutes later)
                    ClockSkew = TimeSpan.Zero
                }, out SecurityToken validatedToken);

                var jwtToken = (JwtSecurityToken)validatedToken;
                var accountId = int.Parse(jwtToken.Claims.First(x => x.Type == "id").Value);

                // attach account to context on successful jwt validation
                context.Items["Account"] = await dataContext.Accounts.FindAsync(accountId);
            }
            catch 
            {
                // do nothing if jwt validation fails
                // account is not attached to context so request won't have access to secure routes
                Console.WriteLine("Failed");
            }

        

So on the server side I have controller that has [Authorize(Role.Admin)] annotation like below which I can't understand - how Authorize can understand the Role:Admin - which is application specific - is it via introspection?

[Authorize(Role.Admin)]
        [HttpGet("all-dates")]
        public ActionResult<ScheduleDateTimeResponse> GetAllDates()
        {
            var dates = _accountService.GetAllDates();
            return Ok(dates);
        }