Fix incompatible django version and refactor tests

Fixes #8 (closed)

• Juga refactor test untuk setiap penggunaan content type "multipart/form-data" pada header karena tidak selalu dapat diterima datanya menggunakan request.data, diubah content type nya menjadi "application/x-www-formurlencoded"

  The x-www-form-urlencoded is used more generally to send text data to the server while multipart/form-data is used to send binary data, most notably for uploading files to the server. https://javarevisited.blogspot.com/2017/06/difference-between-applicationx-www-form-urlencoded-vs-multipart-form-data.html