Add Generic version of EntityTypeConfiguration Attribute

[saivineeth100]

Add generic arguments support for EntityTypeConfiguration attribute

From

[EntityTypeConfiguration(typeof(ModelConfiguration))]
    public class Model
    {.....}

To

[EntityTypeConfiguration<ModelConfiguration>()]
    public class Model
    {.....}

[Marusyk]

Should we extend EntityTypeConfigurationEntityTypeAttributeConvention with the new EntityTypeConfigurationAttribute<T> or create a new one?

[ajcvickers]

@Marusyk Probably extend, unless that doesn't work very well.

[joelmandell]

Is this one up for grabs?

[ajcvickers]

@joelmandell Yes.

[amyboose]

Useful feature for DDD when parent class is generic Entity or AggregateEntity

[OsamaAbuSitta]

In order to add generic constraint as the below should we move IEntityTypeConfiguration from EFCore to the abstraction project ,
since the type EntityTypeConfigurationAttribute exists in EFCore.Abstractions project , or we move the generic implementation to the EFCore project fix

where TEntity : IEntityTypeConfiguration

[ajcvickers]

@OsamaAbuSitta We will discuss. The problem is that IEntityTypeConfiguration has other dependencies that we cannot move. We may not be able to add a constraint to the generic argument.

[OsamaAbuSitta]

@ajcvickers , In that case, should I proceed with submitting the pull request? for this changes commit