Add the possibility to collapse notifications

[sanderkoenders]

Is your feature request related to a problem? Please describe.
I have been using Gotify for the past couple of weeks and it has been serving me very well. The only minor annoyance I have, which is unrelated to Gotify, is the notifications I receive from my Proxmox backups. It is a very lengthy message because the logs are attached.

Describe the solution you'd like
The solution I was thinking about is adding the possibility to collapse the notification when it is longer than x characters. Ideally there would be a "view more" button that allows to show the collapsed contents.

Describe alternatives you've considered
I have considered turning off Proxmox backup notifications altogether but unfortunately then I would lose the lion share of useful information.

[jmattheis]

👍, seems good, we can probably collapse after 20 or so lines.