1. **Multiselect Support for Choice Fields**
- Added a `multiselect` option to the choices field component
- Updated Field model to accept arrays as values for choices fields
2. **Post Content Feature Filtering**
- Added ability to filter posts based on content features:
- Posts with images
- Posts with links
- Posts with code blocks
- Posts with uploads
3. **Improved Group Filtering**
- Renamed `restricted_user_group` to `restricted_groups` to allow
filtering by multiple groups
- Added `excluded_groups` to replace `ignore_group_members` which was
complex for end users
- Renamed `restricted_groups` to `restricted_inbox_groups` for more
specific PM filtering and clarity.
4. **Public Topics Filter**
- Added a "Public Topics" filter option that excludes all secure
categories
