In a next-gen project when a ticket moves into our Programming In Progress column I want the assignee to automatically get set to the user who is in our custom field called Programmer. I've figured out that the actual name of the field is "customfield_10187".

I've tried the following values in the User field with no luck:
- {{Programmer}}
- {{Programmer[0]}}
- {{Programmer[0].displayName}}
- {{customfield_10187}}
- {{customfield_10187[0]}}
- {{customfield_10187[0].displayName}}
I've also tried using "issue.fields." in front of the above attempts. Since the Programmer field can have multiple programmers listed (actually, we've set it to only allow one for the project, but the field type technically allows for multiples so the json value of the field shows as an array of person objects when looking at the raw data for the issue even though there is only one). I've tried various index values other than 0. I've also tried using the displayName property.
The Audit logs show SUCCESS statuses for the actions, but when you show more detail it also says "Issue already assigned to user"