Describe a time you used OOP to design classes that model contracts between customers and companies.
Implement a concise Python model that represents customers, companies, and contracts, then reports whether each contract is active on a specified date. Use the following signature: def summarize_contracts(contracts, as_of):. Each contract is a dictionary with id, customer, company, start, and end fields, where dates use YYYY-MM-DD; return dictionaries containing each contract id and its status, preserving input order.
def summarize_contracts(contracts, as_of):