Returns a list of missing blobs for the requesting account.

*This endpoint is part of the atproto PDS repository management APIs. Requests usually require authentication (unlike the `com.atproto.sync.*` endpoints), and are made directly to the user's own PDS instance.* *To learn more about calling atproto API endpoints like this one, see the [API Hosts and Auth](/docs/advanced-guides/api-directory) guide.* Returns a list of missing blobs for the requesting account. Intended to be used in the account migration flow.