Allow html feature across the platform for more integrations and customizations

- Messaging: html feature only available with newsletters, not in messaging, wants messaging to have an html editor too

- Documents: can only upload pdf, wants those more customizable and wants to add spots for a signature and see on his end what parents will see and what tools they have without having to send it to a test parent account

- Activities: wants to be able to add his own and customize them (add "location" as a field for example)

BAM 25203732 requested this.