Make Deliver policy configurable

[dhanashritidke11]

Description

This MR adds support for configurable JetStream deliver policies for sensor dependencies. Previously, sensors always used a hardcoded deliver policy when subscribing to JetStream subjects. This change allows users to configure the deliver policy on a per-dependency basis, enabling control over which messages are delivered from JetStream streams.

What's New

Users can now configure the deliverPolicy field in sensor dependencies when using JetStream as the EventBus:

apiVersion: argoproj.io/v1alpha1
kind: Sensor
metadata:
  name: example
spec:
  dependencies:
    - name: test-dep
      eventSourceName: webhook
      eventName: example
      jetStream:
        deliverPolicy: "all"  # New configuration option

Why is this needed?

The current consumer Deliver policy is hardcoded to DeliverNew. While this works well with the our existing DiscardOld+Limits eventbus config, it's not compatible with our proposed WorkQueue+DiscardNew policy and Sensor fails to connect to Eventbus with an error:

Supported Deliver Policies

Based on NATS JetStream documentation:

• all: Start receiving from the earliest available message in the stream
• last: Start with the last message added to the stream, or the last message matching the consumer's filter subject if defined
• new: Start receiving messages created after the consumer was created (currently hardcoded to this)

---

Backward Compatibility

✅ Fully backward compatible - no breaking changes:

• Optional field: The jetStream configuration is completely optional
• Default behavior preserved: When not configured, defaults to "new" policy (same as before)
• Existing sensors work unchanged: Sensors without jetStream config continue to work exactly as before
• No migration required: Existing deployments are unaffected

Migration Path

No migration needed. Users can opt-in to the new feature by adding the jetStream configuration to their sensor dependencies when desired.

---

Test Results

Deliver Policy = All

Deliver Policy = New (Backward compatible)

[abdulazillow]

from description.

Default behavior preserved: When not configured, defaults to "new" policy (same as before)

i think new is default from what i understand

[dhanashritidke11]

Yes, you're correct. Currently, the argo-events code defaults to "new" since it is hardcoded in the project.
However, within Jetstream the default deliver policy is "all" which makes this documentation confusing.

Since we already have jetstream specific documentation in https://github.com/zillow/argo-events/pull/10/files#diff-4ab2c17d34a671056836f0920040e4f28863529225a12dcee63c8faf47e72ea6 I'll remove this section as it's too specific to jetstream to reside in Sensor