Core has undocumented methods

[tcharding]

For some versions there are methods available that are undocumented. For an example see #215. We should come up with an explicit strategy and document it.

Some options:

• We could support and test undocumented methods or not
• We could document undocumented methods or not

I'm leaning towards thinking we should support and test anything that can be done easily (i.e., if its just a matter of running existing tests for a version that has the method but its undocumented). I don't think we should go to any further trouble though (eg if the undocumented method in a version differs from the documented method in another version). Also I do not think we should change the version specific module docs (eg types/src/v17/mod.rs).

[GideonBature]

I partly encountered this issue (which is partially documented) in my own case while investigating the listbanned method. I noticed that it exists and functions correctly in versions v17 to v19, but it is not fully documented in those versions.

To confirm its existence and understand its return value, I had to check the source code from core.

I discovered that the method returns the same result as what is officially documented for v20.

Based on this, I agree that it is safe to support and test undocumented methods that can be done easily.

[jamillambert]

Superseded by #333