Sequence and sequence type in metadata #2151
Description
For event sourced entities and value entities we provide sequence number/revision as the sequence attribute (cloud event extension https://github.com/cloudevents/spec/blob/v1.0.2/cloudevents/extensions/sequence.md ) but we do not have those in the SDK CloudEvent APIs, we should add.
Since not every request where the API is used is from a subscription, if we add getters the result must be optional