Recurring trades as treaty clauses

**What do you want to see?**
A treaty clause for a recurring trade

**How would it help players?**
Give them the ability to set up recurring transfers of resources and things like that, without having to send trades every turn

**Alternatives**
???

**Screenshots and mockups**
N/A

**Things to consider**
What happens if items are not available to transfer? When does this take place in terms of budgeting relative to things like maintenance? Should this be limited to resources or should other things be tradable in this way? How about an option for a finite duration? Maybe a renewal reminder too? Should all treaty clauses have the option for a finite duration?

**Related issues**
N/A