Add a full-featured upload approach to the object service

[djmitche]

#32 implemented a pretty basic upload approach. Let's build that out to support the features we need; as of this writing

• uploader-provided hashes (in Add support for content hashes taskcluster#4608 - this is independent of upload method)
• multipart/parallel uploads
  • this differs per cloud, so we must have cloud-specific upload methods, with a fallback to a common method
• robust retry support (putUrl already supports this)
• object lifecycle (in particular, a not-yet-uploaded state) (this is already done)
• https://bugzilla.mozilla.org/show_bug.cgi?id=1442024 - add refererer-policy headers (https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Referrer-Policy) (Add Referrer-Policy headers to all objects taskcluster#4609)
• Where the cloud cannot cross-encode, require the data have content-encoding: identity so that callers that do not set the Accept-Encoding header do not get an encoded response. (Set Content-Encoding: identity on S3 objects taskcluster#4610)
  • Add a real download approach to the object service #38 (comment) for some research leading to this requirement.

[djmitche]

I don't think this is done -- the putUrl upload method isn't full-featured. Let's use this issue (first comment) to track requirements for upload support, and then break it out either into other epics or other issues.