cleanup: doh.powerdns.org is not working anymore (#924)

While there, `.../internal/sessionresolver` => `.../sessionresolver`

See https://github.com/ooni/probe/issues/2255

internal/engine/netx/dnstransport.go

@@ -24,7 +24,7 @@ import (
 // create the underlying Dialer and/or HTTP transport, if needed. The URL
 // argument describes the kind of client that we want to make:
 //
-// - if the URL is `doh://powerdns`, `doh://google` or `doh://cloudflare` or the URL
+// - if the URL is `doh://google` or `doh://cloudflare` or the URL
 // starts with `https://`, then we create a DoH client.
 //
 // - if the URL is `` or `system:///`, then we create a system client,
@@ -49,8 +49,6 @@ func NewDNSClientWithOverrides(config Config, URL, hostOverride, SNIOverride,
 	// We should split this function in smaller and testable units
 	// TODO(https://github.com/ooni/probe/issues/2121#issuecomment-1147424810)
 	switch URL {
-	case "doh://powerdns":
-		URL = "https://doh.powerdns.org/"
 	case "doh://google":
 		URL = "https://dns.google/dns-query"
 	case "doh://cloudflare":

internal/engine/netx/dnstransport_test.go

@@ -29,22 +29,6 @@ func TestNewDNSClientUnsupportedScheme(t *testing.T) {
 	}
 }
 
-func TestNewDNSClientPowerdnsDoH(t *testing.T) {
-	dnsclient, err := NewDNSClient(
-		Config{}, "doh://powerdns")
-	if err != nil {
-		t.Fatal(err)
-	}
-	r, ok := dnsclient.(*netxlite.SerialResolver)
-	if !ok {
-		t.Fatal("not the resolver we expected")
-	}
-	if _, ok := r.Transport().(*netxlite.DNSOverHTTPSTransport); !ok {
-		t.Fatal("not the transport we expected")
-	}
-	dnsclient.CloseIdleConnections()
-}
-
 func TestNewDNSClientGoogleDoH(t *testing.T) {
 	dnsclient, err := NewDNSClient(
 		Config{}, "doh://google")

internal/engine/session.go

@@ -13,8 +13,8 @@ import (
 	"github.com/ooni/probe-cli/v3/internal/atomicx"
 	"github.com/ooni/probe-cli/v3/internal/bytecounter"
 	"github.com/ooni/probe-cli/v3/internal/engine/geolocate"
-	"github.com/ooni/probe-cli/v3/internal/engine/internal/sessionresolver"
 	"github.com/ooni/probe-cli/v3/internal/engine/probeservices"
+	"github.com/ooni/probe-cli/v3/internal/engine/sessionresolver"
 	"github.com/ooni/probe-cli/v3/internal/kvstore"
 	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"

internal/engine/sessionresolver/integration_test.go

@@ -4,7 +4,7 @@ import (
 	"context"
 	"testing"
 
-	"github.com/ooni/probe-cli/v3/internal/engine/internal/sessionresolver"
+	"github.com/ooni/probe-cli/v3/internal/engine/sessionresolver"
 	"github.com/ooni/probe-cli/v3/internal/kvstore"
 )
 

internal/engine/sessionresolver/resolvermaker.go

@@ -35,8 +35,6 @@ var allmakers = []*resolvermaker{{
 	url: "http3://dns.google/dns-query",
 }, {
 	url: "https://dns.quad9.net/dns-query",
-}, {
-	url: "https://doh.powerdns.org/",
 }, {
 	url: systemResolverURL,
 }, {