Add Column Rule (add_column)

Adds a new column with a specified default value.

Field	Description	Required
column_name	Name of the new column to add	✅ Yes
default_value	Default value for the new column	✅ Yes

Example:

{
    "type": "add_column",
    "column_name": "processed_flag",
    "default_value": true
}

Behavior: Adds a new column processed_flag with default value true for all rows.