AddConfigurationResolver extension method seems to be missing in the licensed version of Component space library obtained from nuget.
The SAML for ASP.NET Core package on www.nuget.org is a trial version. However, the use of AddConfigurationResolver is exactly the same for the trial and licensed versions.
The ExampleServiceProvider project includes a ConfigurationExamples class with an example ISamlConfigurationResolver implementation as well as instructions on registering the implementation.
This is done as follows.
builder.Services.AddSaml().AddConfigurationResolver<ConfigurationExamples.CustomConfigurationResolver>();