The `utils` module uses a convoluted mechanism for filling byte arrays
with random data. The `generate` function can be used directly, making
the `utils` module obsolete.
`nim-websock` suffered from a number of issues that are being addressed:
1. Long messages > `frameSize` (default 1 MB) were split into fragments
of `frameSize` each. However, when a concurrent message is sent, it
may be interleaved among the fragments of an already-sending message.
This is only allowed for control packets without a mux extension.
2. When the WebSocket session is closed, a msg may have been partially
received. This partial frame was reported as a full message, without
indication that the receiving was canceled. This behaviour is fixed
by raising a `WSClosedError` instead of reporting the partial msg.
3. When an individual `send` operation was canceled, it would actually
stop sending the remainder of a potentially partially sent messages.
This would corrupt the stream for concurrent and followup operations.
Cancellation is now inhibited for the message currently sending.
It is still possible to cancel messages that are not yet scheduled.
4. Messages could get reordered when using asynchronous encoders. This
is addressed by delaying followup messages until the current message
is fully encoded and transmitted (except for control packets).
Co-authored-by: Tanguy <tanguy@status.im>
* validate utf8 at the message level
* move utf-8 validation to message
* rename `recv` to `recvMsg`
* add partial frame validation tests
* use `recvMsg` instead of `recv`
