Fix GitHub release assets URL validation (#35287) (#35290)

Backport #35287 by @alexblackie

GitHub changed where the attachments on releases are stored, which means
repo migrations with releases now fail because the redirect URLs don't
match the base URL validation. We need to update the base URL check to
check for the `release-assets` subdomain as well.

Co-authored-by: Alex Blackie <[email protected]>

Author: GiteaBot

services/migrations/github.go

@@ -354,7 +354,8 @@ func (g *GithubDownloaderV3) convertGithubRelease(ctx context.Context, rel *gith
 
 				// Prevent open redirect
 				if !hasBaseURL(redirectURL, g.baseURL) &&
-					!hasBaseURL(redirectURL, "https://objects.githubusercontent.com/") {
+					!hasBaseURL(redirectURL, "https://objects.githubusercontent.com/") &&
+					!hasBaseURL(redirectURL, "https://release-assets.githubusercontent.com/") {
 					WarnAndNotice("Unexpected AssetURL for assetID[%d] in %s: %s", asset.GetID(), g, redirectURL)
 
 					return io.NopCloser(strings.NewReader(redirectURL)), nil