Migration Guide 9.x to 10.0

This release includes the following breaking changes in the API:

• Addition of CreateStream methods to IMediator
• Modification of generic constraint on IPipelineBehavior from where TRequest notnull to where TRequest : IRequest<TResponse>
• Modification of generic constraint on IRequestExceptionHandler from where TRequest notnull to where TRequest : IRequest<TResponse>
• Modification of generic constraint on IRequestPostProcessor from where TRequest notnull to where TRequest : IRequest<TResponse>
• Request types (IRequest, IRequest<TResponse>, IBaseRequest, IStreamRequest<TResponse>, and INotification) moved to the MediatR.Contracts package

For the IMediator change, it will likely only affect manually created implementations for testing purposes.

The modification of the generic constraints affects existing open generic implementations. These will likely need to include an additional constraint:

public class GenericPipelineBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
+    where TRequest : IRequest<TResponse>
{