GraphQL API's setRepositoryEnabled deprecation path

Created by: keegancsmith

We learned that a customer relies on our GraphQL API's setRepositoryEnabled mutation from a custom CLI script to prevent Sourcegraph from showing repos that are actually private and shouldn't be visible to all the customer's employees. It would hurt our chances of success if 3.3 removed setRepositoryEnabled without an alternative. They can achieve the same outcome by editing the external service JSON config via the GraphQL API, but this would require their script to know JSONC (JSON with comments and trailing commas), which would be error-prone for them. Is it possible/planned to preserve the functionality of setRepositoryEnabled in 3.3 and just make it perform the update to the ext svc's exclude property?

Part of #2025 (closed)