Changes to List School Contracts

response property items/free_months list-of-types was widened by adding types number to media type application/json of response 200

the items/free_months/anyOf[subschema #1] response's property type changed from integer to number for status 200

added the optional property items/launch_guarantee to the response with the 200 status

added the optional property items/launch_guarantee_end_date to the response with the 200 status

added the optional property items/billing_rhythm to the response with the 200 status

added the optional property items/levels to the response with the 200 status