Add Streaming Subscription Support

[JoshVanL]

Dapr v1.14 adds support for streaming subscriptions which allows for dynamically subscribing to pubsub topics over a bi-directional gRPC stream. This API is exposed via the SubscribeTopicEventsAlpha1 gRPC API.

On first call, the client sends an InitialRequest containing the pubsub, topic name, etc. From then on, topic event messages are sent from daprd to the client over the stream. The client reports the processing status of this message back to daprd. A message will not be considered processed until the client has responded with this status. There can be multiple in-flight topic messages. Daprd unsubscribes from the topic when the stream is closed.

dapr/go-sdk#578 is a reference implementation for the go-sdk.

[dapr-bot]

This issue has been automatically marked as stale because it has not had activity in the last 60 days. It will be closed in the next 7 days unless it is tagged (pinned, good first issue, help wanted or triaged/resolved) or other activity occurs. Thank you for your contributions.

[dapr-bot]

This issue has been automatically closed because it has not had activity in the last 67 days. If this issue is still valid, please ping a maintainer and ask them to label it as pinned, good first issue, help wanted or triaged/resolved. Thank you for your contributions.