Automated JSON-RPC schema validation on default responses

[kdeme]

It would be possible to create automated tests that verify if JSON-RPC APIs are compliant to the JSON-RPC specs.

Most (all?) specs are written in / using open-rpc and one way to do this could be:

• Pick a call
• grab the schema from the open-rpc.json for the specific call
• validate this schema against the resulting json of the call with for example https://ajv.js.org

There is much more tooling around so perhaps there is something more obvious / commonly used available here.

Of course, the result of calls will depend on the state of the node. But I don't think the goal here is testing all possible outcomes of results but rather quick check if the defaults at least match the specification.

For Fluffy/Portal, it should be noted that there are already quite a bit of tests testing the most often used JSON-RPC calls. However, not in some autogenerated way.