Enforcement of API Protocol versions in Client/Signer/Aggregator

[jpraynaud]

Issue

In order to help signers and client operators know if they are running a stale version of the API protocol and facilitate the overall upgrade process of the nodes, we need to put in place a verification mechanism. This mechanism must be optional, if no version is provider by the HTTP client, the verification is skipped.

We need to have signers and client stop and display an error message requesting for an update of the node in case of incompatible API_VERSION detected between signer & aggregator or client & aggregator.

For instance, the Aggregator could return a specific HTTP error code and this would trigger an exit from the signer/client.

Protocol versions are compatible if they share the same minor.

To do

• If Aggregator version !== Signer/Client version: display an error "You need to upgrade your node to version X.Y"
• If the version is not provided, the version is ignored.
• Add units tests or maybe integration tests
• Maybe add a dev blog post (if it brings added value to SPOs)

Relates to #565