Pull request: all: fix client upstreams, imp code

Updates #3186.

Squashed commit of the following:

commit a8dd0e2cda3039839d069fe71a5bd0f9635ec064
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Fri May 28 12:54:07 2021 +0300

    all: imp code, names

commit 98f86c21ae23b665095075feb4a59dcfcc622bc7
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Thu May 27 21:11:37 2021 +0300

    all: fix client upstreams, imp code

internal/dnsforward/config_test.go

@@ -0,0 +1,53 @@
+package dnsforward
+
+import (
+	"sort"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAnyNameMatches(t *testing.T) {
+	dnsNames := []string{"host1", "*.host2", "1.2.3.4"}
+	sort.Strings(dnsNames)
+
+	testCases := []struct {
+		name    string
+		dnsName string
+		want    bool
+	}{{
+		name:    "match",
+		dnsName: "host1",
+		want:    true,
+	}, {
+		name:    "match",
+		dnsName: "a.host2",
+		want:    true,
+	}, {
+		name:    "match",
+		dnsName: "b.a.host2",
+		want:    true,
+	}, {
+		name:    "match",
+		dnsName: "1.2.3.4",
+		want:    true,
+	}, {
+		name:    "mismatch",
+		dnsName: "host2",
+		want:    false,
+	}, {
+		name:    "mismatch",
+		dnsName: "",
+		want:    false,
+	}, {
+		name:    "mismatch",
+		dnsName: "*.host2",
+		want:    false,
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			assert.Equal(t, tc.want, anyNameMatches(dnsNames, tc.dnsName))
+		})
+	}
+}