Clients should provide a websocket protocol version to specify which version of the Websocket protocol they speak

[cloutiertyler]

John: SpacetimeDB should support reading from a new header, X-Client-Version, which contains the client’s supported SDK version. Important: this version should match the SDK’s supported SpacetimeDB version and may not exactly match the actual SDK version. For example, SDK version 0.5.1, 0.5.1.1 or 0.5.2 might report they support SpacetimeDB version 0.5.1.

Tyler: X-Client-Version <- this is the old way of doing things with custom header names, please check the relevant RFC

[cloutiertyler]

For example, if we make a breaking change to the websocket protocol, we can still support client which connect with the old protocol version.

[cloutiertyler]

This is actually already implemented with the Sec-WebSocket-Protocol header. We currently pass either v1.text.spacetimedb or v1.bin.spacetimedb as the header value. If we make a breaking change, then we can introduce a new version v2.{text/bin}.spacetimedb.

[cloutiertyler]

Closing in favor of: https://github.com/clockworklabs/SpacetimeDBPrivate/issues/984