Add JSON representation of KeyValueEntry

[justenstall]

Proposed change

Update the implementation of jetstream.KeyValueEntry to implement json.Marshaler.

Example implementation to add to the kve type in jetstream/kv.go:

func (e *kve) MarshalJSON() ([]byte, error) {
	return json.Marshal(map[string]any{
		"bucket":   e.Bucket(),
		"key":      e.Key(),
		"value":    string(e.Value()),
		"revision": e.Revision(),
		"created":  e.Created(),
		"delta":    e.Delta(),
		"op":       e.Operation().String(),
	})
}

Use case

Related to nats-io/natscli#1552.

The motivation is to provide a standard JSON representation of the KeyValueEntry information, which would be useful for structured logging and for JSON output from the NATS CLI.

Contribution

Yes

[piotrpio]

@justenstall Thanks for the proposal, this looks good. If you're open to contribute that would be helpful!

[ripienaar]

Be great to also do object

[justenstall]

Be great to also do object

@ripienaar Are you referring to jetstream.ObjectResult or jetstream.ObjectInfo? jetstream.ObjectInfo is already covered by its JSON struct tags.

[ripienaar]

Think we'd need it on ObjectStoreStatus and kv equiv also since no doubt we should support same on kv info etc?

[justenstall]

It would be nice to expose the functionality for external implementations of the interfaces so they can use the standard JSON representation.

Thoughts on exposing this as a KeyValueEntryInfo struct type with JSON tags?