Mainly

BIG improvements to the "Send test notification" button and the notification backend
Fixes for posts:// gets:// notifications
Other minor bug fixes

What's Changed

Fix diff not starting from last viewed snapshot (#2744) by @MoshiMoshi0 in #2856
Remove unused PUID and PGID by @Entepotenz in #2852
Update Apprise to 1.9.2 - Fixes custom posts:// gets:// etc URL's being double-encoded, fixes chantify:// notifications (#2868) (#2875) (#2870)
Follow last_checked time improvements by @dgtlmoon in #2883
"Send test notification" button - improved error handling, code refactor by @dgtlmoon in #2888
Be sure our custom extensions are imported by @dgtlmoon in #2890
Make notifications use quotable URL for better testing by @dgtlmoon in #2870
update linuxserver test build by @dgtlmoon in #2891
Re #2715 add test for new lower higher by @dgtlmoon in #2892

Full Changelog: 0.48.05...0.48.06