Content Delivery API: configuring OAuth

Hi,

We're trying to configure OAuth in our setup of the Content Delivery API, and have followed the instructions in the official documentation for doing so: https://world.episerver.com/documentation/developer-guides/content-delivery-api/configuration/#OAuth 

We have added the EPiServer.ContentApi.OAuth NuGet package, and then added the following line in Startup.cs (as per the official documentation, and also as explained in this accepted answer on the developers forum: https://world.episerver.com/forum/developer-forum/Addons/Thread-Container/2018/11/content-delivery-api---404-on-apiepiserverauthtoken/#199421)

app.UseContentApiIdentityOAuthAuthorization<ApplicationUserManager<ApplicationUser>, ApplicationUser>(new ContentApiOAuthOptions()
{
      RequireSsl = false
});

However, none of the explanations in the referenced links contain information about the implementation of ApplicationUserManager and ApplicationUser. Are we supposed to implement them ourselves? In that case, do you have any documentation on how they should be implemented?

- Thomas