Function get_desired_or_next_id 

pub fn get_desired_or_next_id(
    array: &[Value],
    id_field: &str,
    desired_id: Option<i64>,
    min_value: i64,
) -> Result<i64>

Get the next available ID or use desired ID if specified and available

Matches Python’s getDesiredValueOrNext behavior:

• If desired_id is Some and available, returns it
• If desired_id is Some but taken, returns error
• If desired_id is None, returns next available ID

Arguments

• array - Array of configuration items
• id_field - Name of the ID field (e.g., “DSRC_ID”, “ATTR_ID”)
• desired_id - Optional user-specified ID
• min_value - Minimum value to return (e.g., 1000 for user items)

Returns

ID to use (either desired_id or next available)

Errors

Returns error if desired_id is already taken