Auto-detect content-type in streams #10329
Description
StartExtractForm, ExtractReceipt, and StartExtractLayout all require a FormContentType to be passed in to indicate whether the stream contains a JPG, PNG, etc. We should auto-detect this and possibly allow clients to override (although decide based on our implementation whether they need to do this at all).
The python team is looking at putting this autodetection into their code generator. We should leverage their knowledge in developing a solution for .NET.