web client: use fetch to upload files

also add REST API to upload a single file as POST body

dataprovider/user.go

@@ -348,6 +348,15 @@ func (u *User) GetPermissionsForPath(p string) []string {
 	return permissions
 }
 
+// HasBufferedSFTP returns true if the user has a SFTP filesystem with buffering enabled
+func (u *User) HasBufferedSFTP(name string) bool {
+	fs := u.GetFsConfigForPath(name)
+	if fs.Provider == sdk.SFTPFilesystemProvider {
+		return fs.SFTPConfig.BufferSize > 0
+	}
+	return false
+}
+
 func (u *User) getForbiddenSFTPSelfUsers(username string) ([]string, error) {
 	sftpUser, err := UserExists(username)
 	if err == nil {