Initial implementation of upload files api. (#1703)

* Initial implementation of upload files api.

* Move sanitize method to utils.

* Save uploaded data to uploads folder.

* Avoid loop if we do not have a purpose.

* Minor cleanup of api and fix bug where deleting duplicate filename cause error.

* Revert defer of saving config

* Moved creation of directory to startup.

* Make file names unique when storing on disk.

* Add test for files api.

* Update dependencies.