Returns the substring of a string. Starts with the character at the specified UTF-8 byte index (zero-based) in the string and continues for the specified number of bytes.
3.4
https://www.mongodb.com/docs/manual/reference/operator/aggregation/substrBytes/#mongodb-expression-exp.-substrBytes
Returns the substring of a string. Starts with the character at the specified UTF-8 byte index (zero-based) in the string and continues for the specified number of bytes.