WIP: v1.1.0

Errors resolved

• Fix sitemap and 'preview on page' of partners by fix resolving absolute url for partners (!243 (merged))
• Add missing fancybox images (!244 (merged))
• Fix permissions for sending newsletters ,no longer superuser required (!250 (merged))
• Fix problem with user mailaddress when sending a newsletters (!252 (merged))
• Only show active committees that the user is a member of in events admin, when selecting organisor (!245 (merged))
• Fix check for overlapping memberships and chairs to work correctly (!246 (merged))

New functionality

• Events: add notition that registration is required if you fill in a registration period, otherwise not (!238 (merged))
• Enable fancier permission selection field (!251 (merged))
• Sort committee memberships by starting date on profile page (!255 (merged))
• Add checkbox for the costs warning to newsletter events (!254 (merged))

Technical changes

• Log errors to Slack instead of email (!242 (merged))
• Fix broken migrations for committee chairs (!247 (merged))
• Add management script to clean emails (!253 (merged))