Nats improvement 1545

[davidterins]

Description:

With these changes a consumer of the DotNetCore.CAP.NATS nuget package can opt out from allowing a NATS Consumer client to create topics and streams dynamically which enforces each client to be granted "admin" like permissions. To avoid assigning these permissions to each client, a consumer of the nuget package can now opt out from this by specifying NATSOptions property EnableSubscriberClientStreamAndSubjectCreation to false (defaults to true).

Issue(s) addressed:

• NATS feature: add the possibility to disable dynamic consumer subject/topic creation through NatsCapOtpions #1545

Changes:

• Added new NATSOptions property EnableSubscriberClientStreamAndSubjectCreation and usage of it in NatsConsumerClient.FetchTopics method.
• Added call to OnLogCallback with MqLogType.ConnectError in order to mark the ConsumerRegister as "unhealthy" to allow "subscribe retries" calls to the NatsConsumerClinet.Subscribe method in case the server have not yet configured the expected stream before the client tries to subscribe.

Affected components:

• DotNetCore.CAP.NATS

How to test:

1. Start a nats server (with no configured streams)
2. Start application with a cap subscriber on a specific subject/topic
   Configured with NatsOptions EnableSubscriberClientStreamAndSubjectCreation: false
3. The client will fail to subscribe since the expected stream does not yet exist.
4. Configure the nats server with expected streams and topics expected by application in step 2
5. The application should subscribe to the now configured streams and topics.

Checklist:

• I have tested my changes locally
• I have added necessary documentation (if applicable) (xml summary on public api)
• I have updated the relevant tests (if applicable) (No existing tests for CAP)
• My changes follow the project's code style guidelines

Reviewers:

• @yang-xiaodong

[yang-xiaodong]

LGTM