Update an Opportunity Custom Field

You can rename it, change its type, change whether it accepts multiple values or not, change whether editing its values is restricted to specific Roles, or update the options for a "choices" field type. The updated name will immediately appear in the Close UI and only valid values for the updated `type` will be returned by the Contact API. Some of the type changes need to convert all of the existing values for a given Custom Field to the new type. When this is required, the response will include an additional `converting_to_type` field. When the conversion is done, `converting_to_type` will no longer be returned.