Upload migration archives for GHES and Bitbucket direct to GitHub, rather than going via a blob storage provider

[timrogers]

Description

Migrations from GitHub Enterprise Server (GHES), Bitbucket Server and Bitbucket Data require the data being migrated (a "migration archive") to be uploaded to a blob storage provider, exposing a URL which GitHub.com can use to download the data to continue the migration.

For GHES 3.8+, the GHES applicance itself handles the upload to a configured blob storage provider. For GHES <3.8 and Bitbucket, this CLI does the upload to blob storage.

For some customers, using a public cloud blob storage provider is difficult or possible.

We should switch to data being uploaded to GitHub instead, since the customer trusts GitHub.

[kmaehashi]

Is this feature still unavailable to the public? I saw --use-github-storage option in mentioned in the v1.9.0 release note, but I'm getting this error when I try to use it:

[2025-04-21 14:03:21] [INFO] Uploading archive 2025-04-21_14-03-20-git_archive.tar.gz to GitHub Storage
[2025-04-21 14:03:21] [DEBUG] HTTP POST: https://uploads.github.com/organizations/<org ID>/gei/archive?name=2025-04-21_14-03-20-git_archive.tar.gz
[2025-04-21 14:03:21] [DEBUG] HTTP BODY: BLOB
[2025-04-21 14:03:26] [DEBUG] GITHUB REQUEST ID: XXXX
[2025-04-21 14:03:26] [DEBUG] RESPONSE (NotFound): {"message":"Not Found","request_id":"XXXX","documentation_url":"https://docs.github.com/rest"}
[2025-04-21 14:03:26] [ERROR] [HTTP ERROR 404] System.Net.Http.HttpRequestException: GitHub API error: {"message":"Not Found","request_id":"XXXX","documentation_url":"https://docs.github.com/rest"}