Updates specific fields of an existing solar installation project.

Business Context:
Use this endpoint to modify project details such as financial terms, team assignments,
or project specifications without requiring a full project recreation.

What Can Be Updated:

Financial Terms:

• Agreement type and product type
• Contract values and financing amounts
• Interest rates, escalators, and payment terms
• Down payment and term length

Team Assignments:

• Sales representative assignment
• Dealer assignment
• Installer assignment

Project Details:

• Proposal information and external references
• Project timeline and dates

Business Rules:

• Projects in certain statuses may have restricted update permissions
• Team changes may trigger workflow notifications
• Financial changes may require additional approvals
• Projects must be in "new" status to allow major updates
• If a project is already "in_progress" or later, consider creating a new design instead

Common Use Cases:

• Updating pricing based on final equipment selection
• Reassigning projects to different team members
• Correcting proposal information or external references
• Adjusting payment terms after customer negotiation