Document general required features for SDK

[afrittoli]

From the CDEvent WG meeting on 06 Sept 2022, we discussed general features required by SDKs

• Unit test coverage
• Conformance tests (hosted in the spec/jsonschema?)
• Pin the spec version in the SDK

[afrittoli]

Related to #12

[e-backmark-ericsson]

Should an SDK be able to create events for old versions of the protocol spec, or is it enough that it can only create events with the latest version? What versions of the spec should it be possible to interpret using the SDK on the consumer side?

[afrittoli]

• Support different versions when consuming events

• Do we need to be able to produce old versions of events?

  • Consumers should be able to ignore unknown events / unknown properties i.e. not crash when receiving an event they don't understand

• We should try and parse "future" events as much as possible

• Where parsing an event is not possible, we should try and signal this for DevOps engineer to find out where the parsing failed.

  • We might be able to use CloudEvent response to carry diagnostic info of this kind

[e-backmark-ericsson]

This documentation could also document the general requirements on how to release the SDKs