Feature #484 file support and related http infra improvements

[Syndesi]

Closes #484

[Syndesi]

There should be two more end to end / feature tests as well:

• Upload a binary file in a single request and make sure that the generated sha 256 hash is identical to the file's actual hash, e.g. provided by CLI tools.
• Identical test, just with the file uploaded through multiple requests.

[Syndesi]

Single request Redis keys might use the request id (generated in Caddy) within the Redis value.