This string (followed by a slash '/' character) will be used to prefix each uploaded artifact's file name,
allowing you to form a virtual directory hierarchy. Any combination of characters can be used, but
reserved URL characters must be properly escaped.
Environment variables can also be referenced.
For example: ${BUILD_ID}/${BUILD_NUMBER}/
${BUILD_ID} value will be in the form of YYYY-MM-DD_hh-mm-ss