🎉 Improvements

Display program codes in 'My contributions' (#5573)
Warn when a user cannot create an event in the current category (#5572)
Display all contributions in 'My contributions' and not just those with submitter privileges (#5575)
Apply stronger sanitization on rich-text content pasted into CKEditor (#5560, #5571)
Allow raw HTML snippets when editing custom conference pages and event descriptions (#5584, #5587)
Warn more clearly that link attachments are just a link and do not copy the file (#5551, #5593)
Add option to email people with specific roles about their contributions or abstracts (#5598)
Add setting to allow submitters to edit custom fields in their contributions (#5599)

🐛 Bugfixes

Fix broken links in some notification emails (#5567)
Fix always-disabled submit button when submitting an agreement response on someone's behalf (#5574)
Disallow nonsensical retention periods and visibility durations (#5576)
Fix sorting by program code in editable list (#5582)
Do not strip custom CSS classes from HTML in CKEditor (#5584, #5585)
Use the instance's default locale instead of "no locale" (US-English) in places where no better information is known for email recipients (#5586)