Handle client-server backward incompatible changes #807

At the moment, there is no mechanism to track CLI and server compatibility and handle backward-incompatible changes. This results in the sometimes broken CLI when it works with a newer server version.

We should:

• Handle backward-incompatible changes. The client sends its version to the server via the X-API-Version header. If the server does not support this version, it answers with 412 Precondition Failed. The CLI prints the message asking to update the CLI.
• Reduce the number of backward-incompatible changes. As of now, introducing new fields to common pydantic models is backward-incompatible since models have extra = Extra.forbid set. We can remove this setting if pydantic models used to parse user input (configuration, profile) are decoupled.