- Added new options to allow configuring the maximum number of concurrent connections and upgraded connections.
- `KestrelServerLimits.MaxConcurrentConnections` defaults unlimited.
- `KestrelServerLimits.MaxConcurrentUpgradedConnections` defaults to unlimited.
- Calls to IHttpUpgradeFeature.UpgradeAsync() will throw when the MaxConcurrentUpgradedConnections limit has been reached.
- Kestrel will close new connections without response when MaxConcurrentConnections is reached.