`doi_configured` uses incorrect logic

Currently, we use this `doi_configured` function to check if we should perform DOI operations. However, this function simply checks if _any_ DOI settings are configured, not if they _all_ are. This can lead to errors, since if just a single DOI setting is provided, the application will attempt DOI operations, but will fail, since not all of the settings are configured.

https://github.com/dandi/dandi-archive/blob/f222f03af8ddc1e628fcb0422cabb69ea1c927c7/dandiapi/api/doi.py#L23-L24

Start with dandiapi/api/doi.py at lines 23–24 and inspect how doi_configured determines whether DOI operations run. Confirm the behavior for partial and complete DOI settings; done means DOI operations are skipped unless all required settings are configured, preventing failures from partial configuration.

Written by the indexing model from the issue text.