Searches an array for an occurrence of a specified value and returns the array index of the first occurrence. If the substring is not found, returns -1.
3.4
https://www.mongodb.com/docs/manual/reference/operator/aggregation/indexOfArray/#mongodb-expression-exp.-indexOfArray
Searches an array for an occurrence of a specified value and returns the array index of the first occurrence. If the substring is not found, returns -1.