Function user_field_value 

pub fn user_field_value(raw: &str) -> Value

Translates an accountId-style assignee/reporter input to the JSON shape JIRA expects.

The empty string clears the user (Atlassian’s supported null payload); any other value is wrapped as {"accountId": "<value>"}. The literal -1 is preserved as {"accountId": "-1"}, which JIRA interprets as automatic assignment.