Tiny links with dashes in them fail to convert

Dashes need to be converted to slashes. But then, the base 64 URL decoder we are using to handle non-padded base64 doesn't like the slashes, causing an illegal argument exception.

A solution is to manually pad the tiny url part and then use the regular base64 decoder, like in this Python code:
https://community.atlassian.com/t5/Confluence-questions/Is-there-a-way-to-get-the-page-information-with-the-Confluence/qaq-p/1968227#date-2114987