Stream variable state change event

[salehjafarli]

Description

This is a suggestion pr for resolving issue #25899. It is draft and no testing change made yet demonstrate functionality I need. I did not change state of db purposefully to avoid any breaking change, and current state of streamed event is satisfactory for what I want to achieve. Change in variable will be reflected in events api, and the type of change I can infer from checking variables endpoint(update or delete)

Fixes: #25899
Fixes: https://hashicorp.atlassian.net/browse/NMD-773

Testing & Reproduction steps

Links

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[tgross]

Hi @salehjafarli! This is looking pretty good. I do wonder if for your particular use case described in #25899 if you wouldn't be better off with a blocking query. After all, that's how we watch for changes to specific variables in template blocks. But if you're watching a very large set of variables, I suppose this option makes more sense and it probably doesn't hurt to include it.

In any case, a few things that'll need here:

• We'll definitely need tests.
• We need to make sure we're authenticating access in nomad/stream/event_broker.go, otherwise anyone can read these events.
• We'll need a changelog entry (make cl)
• We'll need documentation updates to the table in website/content/api-docs/events.mdx

The other thing that's odd here is that the CLA bot didn't tag you. Have you previously signed HashiCorp's CLA?

[tgross]

The payload will include the encrypted blob, not the decrypted values. We probably don't want to decrypt here but that also means that we should use the variable metadata struct as the event body rather than the contents.