Greetings,
The V1 report returned via the Extensions Developer Analytics endpoint is now considered deprecated and will be decommissioned on January 13, 2020. On and after this date, the Extension Analytics API will only return the V2 report, which contains 30+ additional data points to monitor the health of your Extensions on Twitch. In addition to the API, developers can access an analytics dashboard via the version management page for any Extension that has been released on Twitch.
There is no change in how the endpoint is used, only the data that is returned. Should you call /helix/analytics/extensions and specify the type=overview_v1 query string parameter on or after the date above, you will receive the following return payload since it will no longer be valid.
{"error":"Bad Request","status":400,"message":"Invalid Report Type"}
If you have any questions, please let us know in the comments.