Requirement for an incentive.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v25/services/incentive_service.proto)

| Fields ||
|---|---|
| ## `requirement` Union field. The requirement for this incentive. Currently only spend requirements are supported, requirements for other actions may be supported in a later version. `requirement` can be only one of the following: ||
| ### `spend` | `https://developers.google.com/google-ads/api/reference/rpc/v25/Incentive.Requirement.Spend` Optional. Spend requirement for an incentive. |