4.0.0a5

• BREAKING Added the cleanup() scheduler method and a configuration option (cleanup_interval). A corresponding abstract method was added to the DataStore class. This method purges expired job results and schedules that have exhausted their triggers and have no more associated jobs running. Previously, schedules were automatically deleted instantly once their triggers could no longer produce any fire times.
• BREAKING Made publishing JobReleased events the responsibility of the DataStore implementation, rather than the scheduler, for consistency with the acquire_jobs() method
• BREAKING The started_at field was moved from Job to JobResult
• BREAKING Removed the from_url() class methods of SQLAlchemyDataStore, MongoDBDataStore and RedisEventBroker in favor of the ability to pass a connection url to the initializer
• Added the ability to pause and unpause schedules (PR by @WillDaSilva)
• Added the scheduled_start field to the JobAcquired event
• Added the scheduled_start and started_at fields to the JobReleased event
• Fixed large parts of MongoDBDataStore still calling blocking functions in the event loop thread
• Fixed JSON serialization of triggers that had been used at least once
• Fixed dialect name checks in the SQLAlchemy job store
• Fixed JSON and CBOR serializers unable to serialize enums
• Fixed infinite loop in CalendarIntervalTrigger with UTC timezone (PR by unights)
• Fixed scheduler not resuming job processing when max_concurrent_jobs had been reached and then a job was completed, thus making job processing possible again (PR by MohammadAmin Vahedinia)
• Fixed the shutdown procedure of the Redis event broker
• Fixed SQLAlchemyDataStore not respecting custom schema name when creating enums
• Fixed skipped intervals with overlapping schedules in AndTrigger (#911 <#911>_; PR by Bennett Meares)
• Fixed implicitly created client instances in data stores and event brokers not being closed along with the store/broker