TODOs

```bash
$ git grep -nw TODO BuildSourceImage.sh
BuildSourceImage.sh:6:# TODO maybe a flag for this?
BuildSourceImage.sh:45: # TODO: maybe this could be individual checks so it can report
BuildSourceImage.sh:267: ## TODO: check for authfile, creds, and whether it's an insecure registry
BuildSourceImage.sh:308: ## TODO: check for authfile, creds, and whether it's an insecure registry
BuildSourceImage.sh:387: # TODO this will need to be refactored when we start seeing +zstd layers.
BuildSourceImage.sh:451: ## TODO: check for authfile, creds, and whether it's an insecure registry
BuildSourceImage.sh:618: # TODO account for "artifact_path" being a directory?
BuildSourceImage.sh:625: # TODO this symlink need to be relative path, not to `/blobs/...`
BuildSourceImage.sh:629: # TODO this symlink need to be relative path, not to `/blobs/...`
BuildSourceImage.sh:685: # TODO account for "artifact_path" being a directory?
BuildSourceImage.sh:692: # TODO this symlink need to be relative path, not to `/blobs/...`
BuildSourceImage.sh:696: # TODO this symlink need to be relative path, not to `/blobs/...`
BuildSourceImage.sh:873: # TODO one day, check and confirm with %{sourcepkgid}
BuildSourceImage.sh:1219: # TODO probably just _error here to exit
BuildSourceImage.sh:1227: # TODO maybe look to a directory like /usr/libexec/BuildSourceImage/drivers/ for drop-ins to run
```
(as of efd2679729edadaacd2e8c26f247b22912910012)