Consider New Ardalis.Result.FastEndpoints package with base classes, extension methods

For example this code from a devBetter.com member:

```csharp
public abstract class EndpointBase : Endpoint where TRequest : notnull where TResponse : notnull where TMapper : class, IResponseMapper
{
public override async Task ExecuteAsync(TRequest req, CancellationToken ct)
{
Result response = await ProcessAsync(req, ct)
.ConfigureAwait(false);

this.AddResultErrors(response);

ThrowIfAnyErrors();

return response
.ToMinimalApiResult();
}

public abstract Task> ProcessAsync(TRequest request, CancellationToken cancellationToken);
}

// or similar by nhwilly
public abstract class EndpointBase : Endpoint where TRequest : notnull where TResponse : notnull
{
public override async Task ExecuteAsync(TRequest req, CancellationToken ct)
{
Result response = await ProcessAsync(req, ct)
.ConfigureAwait(false);

this.AddResultErrors(response);

ThrowIfAnyErrors();

return response.ToMinimalApiResult();
}

public abstract Task> ProcessAsync(TRequest request, CancellationToken cancellationToken);
}
```

Start by reviewing the two proposed EndpointBase examples and the referenced AddResultErrors and ToMinimalApiResult calls. Define the package scope, base-class variants, and extension methods before implementation; done should include an agreed design and corresponding tests.

Written by the indexing model from the issue text.