1.5.5-rc2

What's Changed

• feature: Add new app to store activity assignments (M2-7285) by @rcmerlo in #1511
• fix: allow auto_assign field to be None (M2-7285) by @farmerpaul in #1531
• fix: Hot fix for null auto-assign field in activity flow (M2-7285) by @rcmerlo in #1536

Full Changelog: v1.5.4...v1.5.5-rc2