After thinking a little about this, I don't see what's the point of maintaining the API compatibility here.
We are introducing new dependencies, so we are in fact introducing a backwards-incompatible change.
If we would be sticking to the original compromise of using semantic versioning, I think we should just bump to 0.4.0, backward incompatible change in the client, and that's all.

This manifest the need of having a good conversation about dependency pinning and api compatibility within the client, the client's subprojects, and the webapp and platform.