Review and release beta APIs

Description

The following APIs has been updated to be a part of our supported API:

• Logging (EPiServer.Logging namespace in EPiServer.Framework.dll)
• Notifications (EPiServer.Notification namespace in EPiServer.dll)
• Async tasks (EPiServer.Async namespace in EPiServer.Framework.dll)
• Activities (EPiServer.DataAbstraction.Activities namespace in EPiServer.dll)
• IdentityMappingService (part of EPiServer.DataAbstraction in EPiServer.dll)
• SecurityEntityProvider (part of EPiServer.Security in EPiServer.Framework.dll)
• UrlSegmentOptions (part of EPiServer.Web namespace in EPiServer.dll)
• IContextValidate (part of EPiServer.Framework.Validation namespace in EPiServer.Framework.dll)

As a part of the review of these API the following changes were made:

• The properties ValidUrlCharacters and Encode on type UrlSegmentOptions has been obsoleted and replaced by properties ValidCharacters and SupportIriCharacters
• It is no longer necessary to implement INotificationFormatter when implementing IUserNotificationFormatter.
• Notifications can be sent on a channel without a notification formatter. These notifications will be considered to be user notifications only.
• FormatterName was removed from INotificationFormatter and IUserNotificationFormatter.
• The logic of FindSubscribersAsync in ISubscriptionService has been changed so that it returns all subscribers where the search key starts with the key of the subscription. A ListSubscriptionsAsync has also been added that returns all subscriptions that starts with the key.