Updates specific fields of an existing project adder.

Business Context:
Use this endpoint to modify adder details such as name, quantity, or pricing
as project requirements change or during the estimation and approval process.

What Can Be Updated:

• Name: Description or title of the adder
• Quantity: Number of units or items
• Subtotal: Total cost for the adder
• Metadata: Additional properties and specifications

Update Triggers:

• Pricing Changes: Updated vendor quotes or material costs
• Scope Modifications: Changes in project requirements
• Customer Requests: Additions or modifications to upgrade requests
• Engineering Review: Refined specifications or requirements
• Permit Requirements: Changes due to local code requirements

Business Rules:

• Adders attached to finalized projects may have update restrictions
• Significant cost changes may require customer approval
• Updates may affect project total pricing and financing calculations