feat: add native WebDAV submodule

This commit introduces a new, high-performance, and extensible WebDAV submodule, implemented natively without external dependencies.

The submodule includes:
- A core WebDAV handler that supports essential methods: PROPFIND, MKCOL, GET, PUT, DELETE, COPY, MOVE, LOCK, and UNLOCK.
- An extensible design using a `FileSystem` interface to decouple the protocol logic from the storage backend.
- Two `FileSystem` implementations:
  - `MemFS`: An in-memory, tree-based filesystem for testing and ephemeral storage.
  - `OSFS`: A secure, OS-based filesystem that interacts with the local disk and includes path traversal protection.
- A `LockSystem` interface with an in-memory implementation (`MemLock`) to support resource locking (DAV Class 2).
- Comprehensive unit tests covering all major functionalities.
- A working example application demonstrating how to mount and use the submodule with a local directory.

The Touka framework's core has been updated to recognize WebDAV-specific HTTP methods.

webdav/osfs.go

@@ -0,0 +1,115 @@
+// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+// Copyright 2024 WJQSERVER. All rights reserved.
+// All rights reserved by WJQSERVER, related rights can be exercised by the infinite-iroha organization.
+package webdav
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// OSFS is a WebDAV FileSystem that uses the local OS file system.
+type OSFS struct {
+	RootDir string
+}
+
+// NewOSFS creates a new OSFS.
+func NewOSFS(rootDir string) (*OSFS, error) {
+	rootDir, err := filepath.Abs(rootDir)
+	if err != nil {
+		return nil, err
+	}
+	return &OSFS{RootDir: rootDir}, nil
+}
+
+func (fs *OSFS) resolve(name string) (string, error) {
+	path := filepath.Join(fs.RootDir, name)
+	if !strings.HasPrefix(path, fs.RootDir) {
+		return "", os.ErrPermission
+	}
+	return path, nil
+}
+
+// Mkdir creates a directory.
+func (fs *OSFS) Mkdir(ctx context.Context, name string, perm os.FileMode) error {
+	path, err := fs.resolve(name)
+	if err != nil {
+		return err
+	}
+	return os.Mkdir(path, perm)
+}
+
+// osFile is a wrapper around os.File that implements the File interface.
+type osFile struct {
+	*os.File
+}
+
+// Stat returns the FileInfo structure describing file.
+func (f *osFile) Stat() (ObjectInfo, error) {
+	fi, err := f.File.Stat()
+	if err != nil {
+		return nil, err
+	}
+	return fi, nil
+}
+
+// Readdir reads the contents of the directory associated with file and returns
+// a slice of up to n FileInfo values, as would be returned by Lstat.
+func (f *osFile) Readdir(count int) ([]ObjectInfo, error) {
+	fi, err := f.File.Readdir(count)
+	if err != nil {
+		return nil, err
+	}
+	oi := make([]ObjectInfo, len(fi))
+	for i := range fi {
+		oi[i] = fi[i]
+	}
+	return oi, nil
+}
+
+// OpenFile opens a file.
+func (fs *OSFS) OpenFile(ctx context.Context, name string, flag int, perm os.FileMode) (File, error) {
+	path, err := fs.resolve(name)
+	if err != nil {
+		return nil, err
+	}
+	f, err := os.OpenFile(path, flag, perm)
+	if err != nil {
+		return nil, err
+	}
+	return &osFile{f}, nil
+}
+
+// RemoveAll removes a file or directory.
+func (fs *OSFS) RemoveAll(ctx context.Context, name string) error {
+	path, err := fs.resolve(name)
+	if err != nil {
+		return err
+	}
+	return os.RemoveAll(path)
+}
+
+// Rename renames a file.
+func (fs *OSFS) Rename(ctx context.Context, oldName, newName string) error {
+	oldPath, err := fs.resolve(oldName)
+	if err != nil {
+		return err
+	}
+	newPath, err := fs.resolve(newName)
+	if err != nil {
+		return err
+	}
+	return os.Rename(oldPath, newPath)
+}
+
+// Stat returns file info.
+func (fs *OSFS) Stat(ctx context.Context, name string) (ObjectInfo, error) {
+	path, err := fs.resolve(name)
+	if err != nil {
+		return nil, err
+	}
+	return os.Stat(path)
+}