Sales Management

class Opportunity(CremeEntity):
    """
    Sales opportunity entity for pipeline management.

    Attributes:
    - name: str, opportunity name
    - sales_phase: ForeignKey, current sales phase
    - estimated_sales: DecimalField, potential revenue
    - made_sales: DecimalField, actual revenue
    - closing_date: DateField, expected close date

    Methods:
    - advance_phase(): Move to next sales phase
    - calculate_probability(): Get close probability
    """

class SalesPhase(models.Model):
    """
    Sales phase for opportunity progression.

    Attributes:
    - name: str, phase name
    - order: int, phase sequence order
    - won: bool, indicates successful close
    - lost: bool, indicates lost opportunity
    """