Allow applications to create model building conventions (aka public conventions)

• Create public interfaces for metadata API to be used by conventions.
• Change QueryFilter, DefiningQuery, IsEagerLoaded, IsShadowProperty , IsIndexedProperty, BeforeSaveBehavior AfterSaveBehavior to extension methods.
• Throw when calling SetField would change the shadowness of a property or the name of the identifying MemberInfo.
• Rename GetContainingPrimaryKey to FindContainingPrimaryKey.
• Throw when calling SetField on a shadow or a field-only property.
• Create public interfaces that the internal model builders implement, e.g. IConventionModelBuilder. This will allow cleaner API, without the explicit ConfigurationSource parameter.
• Throw instead of silently failing when a non-explicit configuration call is invalid. This would require adding quiz API (‘CanSet’).
• Make model element references consistent (e.g. Property vs IProperty vs string vs PropertyInfo)
• Add provider-specific extension methods for convention metadata interfaces.
• Rename and move RelationalAnnotations and RelationalAnnotationsBuilder to Core.
• Remove unused methods on provider classes like SqlServerPropertyBuilderAnnotations.ColumnName.
• Rename the Apply methods to be more descriptive and make the return types consistent, still allowing to stop the execution of the following conventions.
• Pass CoreConventionSetBuilderDependencies to the constructor of all conventions.
• Add convention type for configuring a type as owned and use it to remove ambiguous ownerships.
• Track the model elements as they are modified by conventions, so a call to a convention never returns an element that is no longer in the model.
• Add a way to delay the convention execution.
• Move logic from ModelCustomizer to a convention.
• Add SqlServerValueGenerationStrategy.None value that can be used to override the model default.
• Filter out the core annotations changes from conventions.
• Remove PropertyMetadataChanged() calls and don’t cache indexes while the model is mutable.
• Expose conventions as List on ConventionSet
• Add methods to add/remove a convention to/from all appropriate convention lists.
• Add a Conventions property of ConventionSetBuilder type to ModelConfigurationBuilder with methods to add/remove a convention

[AndriySvyryd]

@Saibamen No, we don’t plan to ship this in EF Core 5.0

[ajcvickers]

@IanKemp Yes, some chance.