Downloader: Remove verbose flag (#464)

* Remove verbose flag from downloader.

* Do structured http logging in forwarder, too.

* Use structured logging to separate http traffic of downloader from forwarder.

internal/options/log.go

@@ -0,0 +1,33 @@
+// This file is Free Software under the MIT License
+// without warranty, see README.md and LICENSES/MIT.txt for details.
+//
+// SPDX-License-Identifier: MIT
+//
+// SPDX-FileCopyrightText: 2023 German Federal Office for Information Security (BSI) <https://www.bsi.bund.de>
+// Software-Engineering: 2023 Intevation GmbH <https://intevation.de>
+
+package options
+
+import (
+	"log/slog"
+	"strings"
+)
+
+// LogLevel implements a helper type to be used in configurations.
+type LogLevel struct{ slog.Level }
+
+// MarshalFlag implements [flags.Marshaler].
+func (ll LogLevel) MarshalFlag() (string, error) {
+	t, err := ll.MarshalText()
+	return strings.ToLower(string(t)), err
+}
+
+// UnmarshalFlag implements [flags.Unmarshaler].
+func (ll *LogLevel) UnmarshalFlag(value string) error {
+	var l slog.Level
+	if err := l.UnmarshalText([]byte(value)); err != nil {
+		return err
+	}
+	*ll = LogLevel{Level: l}
+	return nil
+}