Deeplink redirector
Send a link shaped like /<app>/<action>/<path>?<query> and it opens
<app>://<action>/<path>?<query>. Links are signed, and are
generated with tools/deeplink.py.
https://s.pvi.me/obsidian/open?vault=Donorbox&file=Notes%2FT-115.md&_s=…
↓
obsidian://open?vault=Donorbox&file=Notes%2FT-115.md