Implement listbanned method and test

[GideonBature]

The JSON-RPC method listbanned does return a type. We want to test this to catch any changes in behavior in future Core versions.

This PR adds a client function that errors if the return value is anything other than the type it returns, along with an integration test that calls this function.

Ref: #116

[tcharding]

There are a few problems with this one. Primarily the integration test does not test anything because the vector in ListBanned is always empty so the Banned struct is never tested.

Can you fix that up and we'll go from there?

Also:

• the client macro needs underscore in the name
• the last patch should be part of the first

Thanks

[GideonBature]

oh my... Let me fix them up.

[tcharding]

Looking much better man.

[tcharding]

I think something is still wrong here. If I comment out the fields in Banned and run the tests it still passes?

[GideonBature]

Woaw... Let check what is wrong.

[GideonBature]

I think something is still wrong here. If I comment out the fields in Banned and run the tests it still passes?

Thank you for pointing this out. seems the test was only checking if there is at least an element inside of the ListBanned, which would be the Banned entry, but not verifying whether the Banned struct itself contains valid field data. I added an assertion for the address field since it is present across all versions. Still thinking of a more robust way to handle this.