Pull request: 2582 invalid hostname

Merge in DNS/adguard-home from 2582-invalid-hostname to master

Updates #2582.

Squashed commit of the following:

commit 909598dae00588792b092f89c272c4487ba55dd1
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Thu Mar 4 17:32:58 2021 +0300

    all: imp code quality, log changes

commit b3b970803709030c48cfe343b88d73524a043de3
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Thu Mar 4 16:56:28 2021 +0300

    home: add host processing logic

internal/home/clients_test.go

@@ -290,3 +290,29 @@ func TestClientsCustomUpstream(t *testing.T) {
 	assert.Equal(t, 1, len(config.Upstreams))
 	assert.Equal(t, 1, len(config.DomainReservedUpstreams))
 }
+
+func TestProcessHost(t *testing.T) {
+	const (
+		name int = iota
+		host
+		want
+
+		fieldsNum
+	)
+
+	testCases := [][fieldsNum]string{{
+		name: "valid",
+		host: "abc",
+		want: "abc",
+	}, {
+		name: "with_trailing_zero_byte",
+		host: "abc\x00",
+		want: "abc",
+	}}
+
+	for _, tc := range testCases {
+		t.Run(tc[name], func(t *testing.T) {
+			assert.Equal(t, tc[want], sanitizeHost(tc[host]))
+		})
+	}
+}