A simple streaming GridFs storage provider for multer

Usage:

// get dependencies
var Grid = require('gridfs-stream');
var multer= require('multer');

//
var storage = require('@typi/gfs-storage');

var myUpload=multer({
        ...
        storage: storage({
	    //function thay provides some gridfs-stream implementation depnending 
	    //the request and file structure (see multer documentation on _handleFile)
            provider: (req, file)=>...      
		      (req, file, cb)=>...

	    //(optinal) function that generates some additional metadata to 
	    // be stored with the file.
	    // filename and mime-type come directly from request
            metadata: function (req, file){
		// for example:
                return {
                    url: req.originalUrl,
                    user: req.loggedUserId
                }
            }

	    //(optional) chunkSize paramter for the gfs.createWriteStream
	    chunkSize: 256
        })
      }));


...
// use myUpload middleware somewhere:
app.use(myUpload)