Our proxy configuration was historically incorrect, due to which
a lot of customers have that in their setups. As a result, strictly
following the websocket RFC results in a breaking change.
For now, we transparently upgrade the version header to 1.1, if we detect 1.0.
If a client was sending 1.0, it wouldn't have worked anyways because persistent
connections were introduced from 1.1 onwards.
https://mattermost.atlassian.net/browse/MM-33836
```release-note
WebSocket handshakes done with HTTP version lower than 1.1 will result in a warning,
and the server will transparently upgrade the version to 1.1 to comply with the
websocket RFC.
This is done to work around incorrect nginx (and other proxy) configs that do not set
the proxy_http_version directive to 1.1.
This facility will be removed in a future Mattermost version and it is strongly recommended
to fix the proxy configuration to correctly use the websocket protocol.
```
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>
4c5ea07aff