feat: Crypt driver, improve http/webdav handling (#4884)

this PR has several enhancements, fixes, and features:
- [x] Crypt: a transparent encryption driver. Anyone can easily, and safely store encrypted data on the remote storage provider.  Consider your data is safely stored in the safe, and the storage provider can only see the safe, but not your data.
  - [x] Optional: compatible with [Rclone Crypt](https://rclone.org/crypt/). More ways to manipulate the encrypted data.
  - [x] directory and filename encryption
  - [x] server-side encryption mode (server encrypts & decrypts all data, all data flows thru the server)
- [x] obfuscate sensitive information internally
- [x] introduced a server memory-cached multi-thread downloader.
  - [x] Driver: **Quark** enabled this feature, faster load in any single thread scenario. e.g. media player directly playing from the link, now it's faster.
- [x] general improvement on HTTP/WebDAV stream processing & header handling & response handling
  - [x] Driver: **Mega** driver support ranged http header
  - [x] Driver: **Quark** fix bug of not closing HTTP request to Quark server while user end has closed connection to alist

## Crypt, a transparent Encrypt/Decrypt Driver. (Rclone Crypt compatible)

e.g.  
Crypt mount path ->  /vault 
Crypt remote path -> /ali/encrypted
Aliyun mount paht -> /ali

when the user uploads a.jpg to /vault, the data will be encrypted and saved to /ali/encrypted/xxxxx. And when the user wants to access a.jpg,  it's automatically decrypted, and the user can do anything with it.
Since it's Rclone Crypt compatible, users can download /ali/encrypted/xxxxx  and decrypt it with rclone crypt tool. Or the user can mount this folder using rclone, then mount the decrypted folder in Linux...

NB.  Some breaking changes is made to make it follow global standard, e.g. processing the HTTP header properly.

close #4679 
close #4827 

Co-authored-by: Sean He <866155+seanhe26@users.noreply.github.com>
Co-authored-by: Andy Hsu <i@nn.ci>

pkg/http_range/range.go

@@ -4,6 +4,7 @@ package http_range
 import (
 	"errors"
 	"fmt"
+	"net/http"
 	"net/textproto"
 	"strconv"
 	"strings"
@@ -12,7 +13,7 @@ import (
 // Range specifies the byte range to be sent to the client.
 type Range struct {
 	Start  int64
-	Length int64
+	Length int64 // limit of bytes to read, -1 for unlimited
 }
 
 // ContentRange returns Content-Range header value.
@@ -22,7 +23,7 @@ func (r Range) ContentRange(size int64) string {
 
 var (
 	// ErrNoOverlap is returned by ParseRange if first-byte-pos of
-	// all of the byte-range-spec values is greater than the content size.
+	// all the byte-range-spec values is greater than the content size.
 	ErrNoOverlap = errors.New("invalid range: failed to overlap")
 
 	// ErrInvalid is returned by ParseRange on invalid input.
@@ -105,3 +106,33 @@ func ParseRange(s string, size int64) ([]Range, error) { // nolint:gocognit
 	}
 	return ranges, nil
 }
+
+func (r Range) MimeHeader(contentType string, size int64) textproto.MIMEHeader {
+	return textproto.MIMEHeader{
+		"Content-Range": {r.contentRange(size)},
+		"Content-Type":  {contentType},
+	}
+}
+
+// for http response header
+func (r Range) contentRange(size int64) string {
+	return fmt.Sprintf("bytes %d-%d/%d", r.Start, r.Start+r.Length-1, size)
+}
+
+// ApplyRangeToHttpHeader for http request header
+func ApplyRangeToHttpHeader(p Range, headerRef *http.Header) *http.Header {
+	header := headerRef
+	if header == nil {
+		header = &http.Header{}
+	}
+	if p.Start == 0 && p.Length < 0 {
+		header.Del("Range")
+	} else {
+		end := ""
+		if p.Length >= 0 {
+			end = strconv.FormatInt(p.Start+p.Length-1, 10)
+		}
+		header.Set("Range", fmt.Sprintf("bytes=%v-%v", p.Start, end))
+	}
+	return header
+}

pkg/utils/io.go

@@ -3,7 +3,10 @@ package utils
 import (
 	"bytes"
 	"context"
+	"fmt"
+	log "github.com/sirupsen/logrus"
 	"io"
+	"time"
 )
 
 // here is some syntaxic sugar inspired by the Tomas Senart's video,
@@ -135,3 +138,29 @@ func (mr *MultiReadable) Close() error {
 	}
 	return nil
 }
+
+type nopCloser struct {
+	io.ReadSeeker
+}
+
+func (nopCloser) Close() error { return nil }
+
+func ReadSeekerNopCloser(r io.ReadSeeker) io.ReadSeekCloser {
+	return nopCloser{r}
+}
+
+func Retry(attempts int, sleep time.Duration, f func() error) (err error) {
+	for i := 0; i < attempts; i++ {
+		fmt.Println("This is attempt number", i)
+		if i > 0 {
+			log.Println("retrying after error:", err)
+			time.Sleep(sleep)
+			sleep *= 2
+		}
+		err = f()
+		if err == nil {
+			return nil
+		}
+	}
+	return fmt.Errorf("after %d attempts, last error: %s", attempts, err)
+}