BE: Added minio to backend and modified jwt-utils

Added minio to backend and modified jwt-utils to extract the key(generated the same all the time) from minio-storage. To run you need to use docker-compose up to open the minio container(you must have docker desktop running). To add a file : http://localhost:8080/api/v1/minio/upload/ , after it you can create folders by simply specifying the folder(can create n folders simultaneously) and the file name last(it`s a POST), and to download http://localhost:8080/api/v1/minio/download/ and filename(including the folders)(GET)