dac-gdac file transfer : add s3 protocol

[tcarval]

To push DAC NetCDF files to GDAC, three file transfer protocols are available: FTP, SFTP, and S3.

• US-GDAC: SFTP only
• Coriolis GDAC: FTP and S3
  Individual DACs can switch from FTP to S3 protocol when transferring to Coriolis GDAC.

DAC using S3 instead of FTP towards Coriolis GDAC

• AOML, from 2025-11-07
• MEDS
• ...

[jnair-argo]

Thanks for making this happen, Thierry & team!