Update the infrastructure for single result specifications.

[fiseni]

Closes #242. Refer to the related issue for more details.

• Added the ISingleResultSpecification<T, TResult> interface.

  public interface ISingleResultSpecification
  {
  }
  public interface ISingleResultSpecification<T> : ISpecification<T>, ISingleResultSpecification
  {
  }
  public interface ISingleResultSpecification<T, TResult> : ISpecification<T, TResult>, ISingleResultSpecification
  {
  }

• Added the SingleResultSpecification base classes for convenience.

  public class SingleResultSpecification<T> : Specification<T>, ISingleResultSpecification<T>
  {
  }
  public class SingleResultSpecification<T, TResult> : Specification<T, TResult>, ISingleResultSpecification<T, TResult>
  {
  }

• Removed the constraints for GetBySpec repository method. Marked these methods as obsolete.

  [Obsolete]
  Task<T?> GetBySpecAsync(ISpecification<T> specification, CancellationToken cancellationToken = default);

  [Obsolete]
  Task<TResult?> GetBySpecAsync<TResult>(ISpecification<T, TResult> specification, CancellationToken cancellationToken = default);

• Added verbose repository methods.

  // These will work with any specification.
  Task<T?> FirstOrDefaultAsync(ISpecification<T> specification, CancellationToken cancellationToken = default);
  Task<TResult?> FirstOrDefaultAsync<TResult>(ISpecification<T, TResult> specification, CancellationToken cancellationToken = default);

  // These will work only with SingleResultSpecification 
  Task<T?> SingleOrDefaultAsync(ISingleResultSpecification<T> specification, CancellationToken cancellationToken = default);
  Task<TResult?> SingleOrDefaultAsync<TResult>(ISingleResultSpecification<T, TResult> specification, CancellationToken cancellationToken = default);

• Added UpdateRangeAsync repository method (community request).

  Task UpdateRangeAsync(IEnumerable<T> entities, CancellationToken cancellationToken = default);

[ardalis]

Looks great!

[davidhenley]

Does this mean GetBySpecAsync should be replaced with First/SingleOrDefaultAsync?

Just making sure as it's not stated anywhere in the release notes

[ardalis]

Yes, and I'll try and get the release notes updated.