Webhooks for syncing and automation

[subdavis]

This is my attempt at a preliminary solution to #573. That's a pretty popular issue, and I think it deserves to be addressed.

See my comment on the issue for more details: #573 (comment)

Adds new config, example:

webhooks:
- url: http://target.url/endpoint
  authorization: "Token iuaorfjaljinfilauhiolkjsnaliufvwqier"
  categories:
  - dns_config
  - dns_rewrite
  - filter

I've opened this issue to start a discussion with the maintainers, but if it makes sense to do something like this, we still need

• tests
• documentation
• UI support (maybe we can push this off for now?)

I've also created https://github.com/subdavis/adguardhome-sync as a proof-of-concept microservice to subscribe to these webhooks and propagate updates. I think the cleverness of that project comes from using TypeScript together with openapi-generator so that future API changes will be detectable at build-time, making it easy to maintain.

EDIT: removed DRAFT status to avoid confusion. Even though this is a work in progress, I'm asking for feedback now.

[ameshkov]

Hi @subdavis, thank you for the PR, and sorry for the late reply and for messing it up by my refactoring:(

Could you please explain why do you need webhooks and how you're going to use it?

[ameshkov]

Ah, my bad, I see why. Let me please think about it a little bit.

[subdavis]

I lost interest, sorry.

FWIW, I think this was the correct approach. It doesn't make sense to have users pushing and pulling entire configuration files when all they wanted to do was make 2 instances enable and disable in unison or synchronize block lists. It also doesn't really make sense to me to discard information about the event source: in all observer/observable patterns, event source is the most important piece of data, and removing it would really just result in users relying on other leaky abstractions to make a best guess at what the event source was.

Maybe PiHole, AdGuard Home, Blocky, or something else will eventually support this.