Add a /config endpoint

[iffyio]

That returns a JSON of the current config the proxy is running with

This includes a breaking change, as the FilterFactory to now needs to return
the config in addition to the filter it created.

Resolves #394

[iffyio]

example output

{
  "clusters": [
    {
      "name": "default-quilkin-cluster",
      "endpoints": [
        {
          "address": "127.0.0.1:4321",
          "metadata": {
            "quilkin.dev": {
              "tokens": [
                "AA=="
              ]
            }
          }
        }
      ]
    }
  ],
  "filterchain": {
    "filters": [
      {
        "name": "quilkin.extensions.filters.capture_bytes.v1alpha1.CaptureBytes",
        "config": {
          "metadataKey": "quilkin.dev/captured_bytes",
          "remove": true,
          "size": 1,
          "strategy": "SUFFIX"
        }
      },
      {
        "name": "quilkin.extensions.filters.token_router.v1alpha1.TokenRouter",
        "config": {
          "metadataKey": "quilkin.dev/captured_bytes"
        }
      }
    ]
  }
}

[iffyio]

Also this has a bunch of conflicts with #395 in the custom filter doc at least, I'll resolve them after that's merged

[XAMPPRocky]

Looks good to me, mostly just minor naming concerns, some code changes, and some potential improvements that can come later.

[XAMPPRocky]

This doesn't have to be in this PR, but I would like to combine these two type parameters into single trait, so that we can enforce it as part of the type system. Then you also only need to provide a single parameter.

trait FilterConfig {
   type Dynamic: prost::Message + Default;
   type Static: serde::Serialize
             + for<'de> serde::Deserialize<'de>
             + TryFrom<Self::Dynamic, Error = ConvertProtoConfigError>;
}

// src/filters/debug.rs
impl FilterConfig for Config {
    type Static = Self;
    type Dynamic = ProtoDebug;
}

[markmandel]

That's pretty, I like it! 👍🏻

[markmandel]

Since #395 is about ready to be merged (I need to make a small change, and it's good to go) -- since this is a particularly useful feature, should we wait until it's merged and bundle it into the 0.2.0 release? (I'm leaning towards "yes", personally)

[iffyio]

Since #395 is about ready to be merged (I need to make a small change, and it's good to go) -- since this is a particularly useful feature, should we wait until it's merged and bundle it into the 0.2.0 release? (I'm leaning towards "yes", personally)

yes please 🙏 also so we can avoid using a custom branch in our deployment internally until the next release

[markmandel]

Added to the milestone!

[markmandel]

Looks great to me!

If @XAMPPRocky is also happy, I'm very happy to have this merged 🥳

[markmandel]

That's pretty, I like it! 👍🏻

[markmandel]

I really like this being back in - since it slowly introduces people to the config option, and then we can move into deserialize, which is the more complex topic. 👍🏻