Describe the bug

When creating a meeting I was able to save it even if I filled the body with capital letters only. Also, the user can save the meeting even if the body is not starting with a capital letter. This is always happening, no matter if the rich text editor is enabled or not.

To Reproduce

1. Log in as admin and activate/deactivate the rich text editor (Organization settings -> Enable rich text editor for participants)
2. Visit the main site
3. Create a meeting
4. Complete all the mandatory fields and fill the body with only capital letters/a text not starting with a capital letter
5. Save

Expected behavior

The user should not be able to save the meeting if there are too many capital letters or the text is not starting with a capital letter in the body and an error should be displayed.

E.g. Proposal creation form:

Screenshots

Stacktrace

No response

Extra data

Tested on nightly

Additional context

No response