Invoke API

[denismakogon]

Moving Invoke API from CLI to fn_go (where it belong).

Changes being made:

• extending provider interface with Invoke method
• Invoke method signature is different from what it was in CLI (see changes to headers and no method thing)

Purpose of this change is not to move away from the CLI as a dependency within Golang apps where I'd like to use providers from fn_go and call functions with authorization.

[rdallman]

this makes me curious about divergence from being generated bindings and I'm guessing this wasn't generated from a swagger file from the looks of it - am generally unclear on how to fix the situation but expressing some desire to generate most of this library from swagger

[denismakogon]

I don’t think that we can generate this type of code, I’m not sure that we can generate providers from swagger.
As far as I understand swagger code gen it can generate only ReST API models and HTTP methods to work with models, but the rest of the code is our own responsibility.