Refactor other parts of Mesh object to be consistent with CA

[jakubdyszkiewicz]

Summary

This PR refactors other parts of the Mesh to be consistent with new CA format. It looks like this

  type: Mesh
  name: mesh1
  logging:
    defaultBackend logstash
    backends:
      - name: logstash
        type: tcp
        config:
          address: 127.0.0.1:5000
      - config:
          path: /tmp/service.log
        type: file
        name: file
  metrics:
    enabledBackend: prometheus-1
    backends:
      - name: prometheus-1
        type: prometheus
        config:
          path: /non-standard-path
          port: 1234
      - name: prometheus-2
        type: prometheus
        config:
          path: /non-standard-path
          port: 1235
  mtls:
    enabledBackend: builtin-1
    backends:
      - name: builtin-1
        type: builtin
      - name: builtin-2
        type: builtin
  tracing:
    defaultBackend: zipkin-us
    backends:
      - name: zipkin-us
        type: zipkin
        config:
          url: http://zipkin.us:8080/v1/spans
      - name: zipkin-eu
        type: zipkin
        config:
          url: http://zipkin.eu:8080/v1/spans

This format will also give us a space to introduce pluggable backends in the future (for metrics, tracing, logging).

Also as a part of this PR I removed injecting Prometheus annotations

	prometheusScrape = "prometheus.io/scrape"	
	prometheusPath   = "prometheus.io/path"	
	prometheusPort   = "prometheus.io/port"	

as it's pretty useless since we need extra tags from kuma-prometheus-sd for our dashboards.

[lobkovilya]

Please feel free to decline any of my suggestions about English.
Maybe a passive voice will sound better here: Kuma is shipped with 'zipkin'

[jakubdyszkiewicz]

We have several expressions "Kuma ships with..." in the docs. I'm not sure which one is correct, I'll stick with the doc version for now.

[lobkovilya]

func validateLoggingTcp(cfgStr *structpb.Struct) validators.ValidationError {
	var verr validators.ValidationError
	cfg := mesh_proto.TcpLoggingBackendConfig{}
	if err := proto.ToTyped(cfgStr, &cfg); err != nil {
		verr.AddViolation("", fmt.Sprintf("could not parse config: %s", err.Error()))
		return verr
	} 

	if cfg.Address == "" {
		verr.AddViolation("address", "cannot be empty")
		return verr
	} 
	
	host, port, err := net.SplitHostPort(cfg.Address)
	if host == "" || port == "" || err != nil {
		verr.AddViolation("address", "has to be in format of HOST:PORT")
	}

	return verr
}

If I'm correct this is the same method but feels more readable to me because of less nesting. Please consider using

[jakubdyszkiewicz]

The problem is that it's not the same. With your suggestion we validate regardless if the config is completely broken (not convertible to a type). I wanted to avoid that

[lobkovilya]

But if it is broken we just return verr:

if err := proto.ToTyped(cfgStr, &cfg); err != nil {
	verr.AddViolation("", fmt.Sprintf("could not parse config: %s", err.Error()))
	return verr
} 

[jakubdyszkiewicz]

ah, I see. Ok, let me change it then

[lobkovilya]

Here I also don't insist, that's up to you, but less nesting looks better to me:

func validateZipkin(cfgStr *structpb.Struct) validators.ValidationError {
	var verr validators.ValidationError
	cfg := mesh_proto.ZipkinTracingBackendConfig{}
	if err := proto.ToTyped(cfgStr, &cfg); err != nil {
		verr.AddViolation("", fmt.Sprintf("could not parse config: %s", err.Error()))
		return verr
	}

	if cfg.ApiVersion != "" && cfg.ApiVersion != "httpJsonV1" && cfg.ApiVersion != "httpJson" && cfg.ApiVersion != "httpProto" {
		verr.AddViolation("apiVersion", fmt.Sprintf(`has invalid value. %s`, AllowedValuesHint("httpJsonV1", "httpJson", "httpProto")))
	}

	if cfg.Url == "" {
		verr.AddViolation("url", "cannot be empty")
		return verr
	} 

	uri, err := url.ParseRequestURI(cfg.Url)
	if err != nil {
		verr.AddViolation("url", "invalid URL")
	} else if uri.Port() == "" {
		verr.AddViolation("url", "port has to be explicitly specified")
	}

	return verr
}

[jakubdyszkiewicz]

same as above