Build a salesforce plugin

Dropcontact is a startup located in Paris, France, inside Station F, the biggest startup campus in the world. We correct, enrich & sync contacts databases with an automated workflow. In order to leverage Salesforce users market, we would like to hire a salesforce plugin developper. Goal : Make our process available to all Salesforce users throught a plugin they could use / connect to their existing contacts database Expected timeframe : 2-4 weeks Expected workflow : Take contacts data from salesforce user database Send them as a file to our api Retrieve the updated file (or provide an url callback) Update contacts accordingly (adding new fields when necessary) Send a feedback if the process was succesfull or not The plugin should be able to receive a file or provide an api access point to update existing contacts Required features : Handle authorizations correctly depending on profiles and roles (read / write), as we need to update (= write) contacts, and not only read them. Delivery : A working plugin integrated in Salesforce A way to test the integration