Error hosting web API in Blazor server web application - asp.net-core

Question

We have an existing .NET 5.0 Blazor web application. I have added an ASP.NET Core Web API to the same project because I want to provide a REST interface to external consumers. When I request http://localhost:5000/stripe/customerwebhook, I get a 404 not found error. What could I be missing?
My CustomerWebhookController API class looks like the following:
[Route("stripe/[controller]")]
[ApiController]
public class CustomerWebhookController : ControllerBase
{
[HttpPost]
public async Task<IActionResult> Index()
{
return Ok();
}
}
Startup.cs:
using Microsoft.AspNetCore.Mvc;
public partial class Startup
{
public void ConfigureServices(IServiceCollection services)
{
OnConfiguringServices(services);
services.AddHttpContextAccessor();
services.AddScoped<HttpClient>(serviceProvider =>
{
var uriHelper = serviceProvider.GetRequiredService<NavigationManager>();
return new HttpClient
{
BaseAddress = new Uri(uriHelper.BaseUri)
};
});
services.AddHttpClient();
services.AddAuthentication();
services.AddAuthorization();
services.AddControllersWithViews();
services.AddMvc(options => options.EnableEndpointRouting = false)
.SetCompatibilityVersion(CompatibilityVersion.Version_3_0);
services.AddRazorPages();
services.AddServerSideBlazor().AddHubOptions(o =>
{
o.MaximumReceiveMessageSize = 10 * 1024 * 1024;
});
}
public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ApplicationIdentityDbContext identityDbContext)
{
OnConfiguring(app, env);
if (env.IsDevelopment())
{
Microsoft.IdentityModel.Logging.IdentityModelEventSource.ShowPII = true;
app.UseDeveloperExceptionPage();
}
else
{
app.Use((ctx, next) =>
{
return next();
});
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseCookiePolicy();
app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();
app.UseMvcWithDefaultRoute();
app.UseEndpoints(endpoints =>
{
endpoints.MapControllerRoute(
name: "default",
pattern: "{controller=Home}/{action=Index}/{id?}");
endpoints.MapControllers();
endpoints.MapBlazorHub();
endpoints.MapFallbackToPage("/_Host");
});
}
}