feat: s3 server support (#6088 close #5186)

Currently tested: List, Get, Remove

server/s3/ioutils.go

@@ -0,0 +1,36 @@
+// Credits: https://pkg.go.dev/github.com/rclone/rclone@v1.65.2/cmd/serve/s3
+// Package s3 implements a fake s3 server for alist
+package s3
+
+import "io"
+
+type noOpReadCloser struct{}
+
+type readerWithCloser struct {
+	io.Reader
+	closer func() error
+}
+
+var _ io.ReadCloser = &readerWithCloser{}
+
+func (d noOpReadCloser) Read(b []byte) (n int, err error) {
+	return 0, io.EOF
+}
+
+func (d noOpReadCloser) Close() error {
+	return nil
+}
+
+func limitReadCloser(rdr io.Reader, closer func() error, sz int64) io.ReadCloser {
+	return &readerWithCloser{
+		Reader: io.LimitReader(rdr, sz),
+		closer: closer,
+	}
+}
+
+func (rwc *readerWithCloser) Close() error {
+	if rwc.closer != nil {
+		return rwc.closer()
+	}
+	return nil
+}