I/O port descriptors w/ file ports

[pcrespov]

When a service has files as ports, the schema only defines a string.
Nonetheless, a file is not simply a type but some sort of reference to a data bump.
A file can be passed as a reference e.g. http/s3/... url, path, api reference. It might also be possible to upload its content (e.g. single/multipart upload). The question is, how should this be described in the ports descriptor? mimetype is definitively something to add but it is not enough. Also, the schema could refer to "syntax of the content".

• Ports with files
• Expose to python client

Follows up from #686

Hi @pcrespov, regarding your question if we should consider this milestone completed: this is the feedback from EN: "from the point of view of the sparc milestones, we consider it complete. however, for our own needs, we will need to finalize that implementation."

I'd proposed to create a new issue, if you want, with the remaining points and close this one.

fyi, the work done was reported to the NIH in the Q1 Report (I can provide you the link if you're interested).

Originally posted by @elisabettai in #686 (comment)