Add MIME type when uploading to S3

[skauk]

Important when hosting files in a public bucket. It was an issue for me when using with Cloudflare R2.

[mxpv]

hmm. I wonder if we should just get mime type from a file extension like this:

      // Determine MIME type from file extension
      contentType := mime.TypeByExtension(filepath.Ext(file))
      if contentType == "" {
          contentType = "application/octet-stream" // fallback
      }

which is much simpler and doesn't introduce new dependencies.

[skauk]

Possible but this approach has limited list of supported types, especially when it comes to media formats. The library on the other hand is solid and handles the job quite well.

[skauk]

@mxpv Since I see some activity, want to remind about this one. I have been using podsync with Cloudflare R2 and a custom audio format for the last few months, and it appears to work fine.