We have just unlocked Romulan Embassy's Recruit Tier I, which means everyone gets to buy an additional Duty Officer Assignment Slot for 50,000 fleet credits! That is, you will get 21 assignments instead of just the usual 20 assignment slots.
How to claim:
1) Visit our Romulan Embassy on New Romulus
2) Find the Turbolift, use it to get to the Shuttlebay
3) Find a console called "Requisition Consumables"
4) Open the consumables store (yes, its confusing) and select "Assignment Slots"
5) Select "+1 Active Duty Officer Assignment Slot" and click buy.