[feature] enable + document explicit IP dialer allowing/denying (#1950)

* [feature] enable + document explicit IP dialer allowing/denying

* lord have mercy

* allee jonge

* shortcut check ipv6 prefixes

* comment

* separate httpclient_test, export Sanitizer

internal/config/util.go

@@ -0,0 +1,39 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package config
+
+import (
+	"net/netip"
+
+	"github.com/superseriousbusiness/gotosocial/internal/log"
+)
+
+func MustParseIPPrefixes(in []string) []netip.Prefix {
+	prefs := make([]netip.Prefix, 0, len(in))
+
+	for _, i := range in {
+		pref, err := netip.ParsePrefix(i)
+		if err != nil {
+			log.Panicf(nil, "error parsing ip prefix from %q: %v", i, err)
+		}
+
+		prefs = append(prefs, pref)
+	}
+
+	return prefs
+}