Add WebAuthn / Passkey integration

This is a rebase of #1618 in which @dave-atx added WebAuthn support.

Closes #1618

internal/model/webauthn.go

@@ -0,0 +1,52 @@
+// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package model // import "miniflux.app/v2/internal/model"
+
+import (
+	"database/sql/driver"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/go-webauthn/webauthn/webauthn"
+)
+
+// handle marshalling / unmarshalling session data
+type WebAuthnSession struct {
+	*webauthn.SessionData
+}
+
+func (s WebAuthnSession) Value() (driver.Value, error) {
+	return json.Marshal(s)
+}
+
+func (s *WebAuthnSession) Scan(value interface{}) error {
+	b, ok := value.([]byte)
+	if !ok {
+		return errors.New("type assertion to []byte failed")
+	}
+
+	return json.Unmarshal(b, &s)
+}
+
+func (s WebAuthnSession) String() string {
+	if s.SessionData == nil {
+		return "{}"
+	}
+	return fmt.Sprintf("{Challenge: %s, UserID: %x}", s.SessionData.Challenge, s.SessionData.UserID)
+}
+
+type WebAuthnCredential struct {
+	Credential webauthn.Credential
+	Name       string
+	AddedOn    *time.Time
+	LastSeenOn *time.Time
+	Handle     []byte
+}
+
+func (s WebAuthnCredential) HandleEncoded() string {
+	return hex.EncodeToString(s.Handle)
+}