77914: Update S3 logic to add custom metadata

[balexandr]

Summary

Pega requested that we add the form's metadata into the S3 call (put_obect()) so they can pull it out on their end.

• Updated S3 service to use put_object() instead of upload_file()
• Add sponsor info to metadata
• Update S3 spec

Related issue(s)

• https://github.com/department-of-veterans-affairs/va.gov-team/issues/77914

Testing done

• Ran automated tests
• Used this to check after putting it up:

response = s3.bucket(bucket_name).object(File.basename(file_path)).get
puts "Metadata: #{response.metadata}"