Shortly after the release of AdWords API v201802, review extensions will be sunset from both extension settings services and feed services for all API versions.

What will happen?
For extension settings services (AdGroupExtensionSettingService, CampaignExtensionSettingService, CustomerExtensionSettingService):

• You will not be able to create a new ReviewFeedItem using any of the extension settings services.
• No ReviewFeedItems will be returned for get() or query() requests to any of the extension settings services.

For feed services (FeedService, FeedItemService, FeedMappingService):

• You will not be able to pass ID 8 to placeholderType of FeedMapping when creating a new feed mapping.
• Feeds, feed items and feed mappings related to review extensions will still be returned for get() or query() requests to FeedService, FeedItemService and FeedMappingService, respectively.

For CampaignFeedService, AdGroupFeedService and CustomerFeedService:

• You will not be able to pass ID 8 to placeholderType of CampaignFeed, AdGroupFeed or CustomerFeed.
• All CampaignFeed, AdGroupFeed and CustomerFeed that are associated with review extensions (have ID 8 in their placeholderTypes) will not be returned for get() or query().

Note that you can still find historical stats for your review extensions after the sunset in PLACEHOLDER_REPORT and PLACEHOLDER_FEED_ITEM_REPORT.

What should you do?
If you have code that retrieves, adds or updates review extensions using any services above, please review your code before March 1 to ensure that the changes above won’t have a negative impact on your application.

As always, if you have any questions, please post on the forum.
 - Thanet Praneenararat, AdWords API Team

Source: Google Ads Developer Blog