Safari doesn't implement filtered drawing on HTML canvas,
it silently ignores the "filter" property of Context2D.
We implement our own blurring by scaling the background down
and then back up.

Also close the stream when we leave.

This hasn't been needed for a long time.

For now, we only reject usernames that might lead to path traversal.
Thanks to Stefan Vinck of Radically Open Security.

We used to only forbid them under Windows.

Thanks to Stefan Vinck of Radically Open Security.

Thanks to Stefan Vinck of Radically Open Security.

Thanks to Baptiste Daroussin.

We were correctly clearing the chat on the server side, but
we were leaving stray entries in the client.

Thanks to J.-J. Sarton.

Thanks to J.-J. Sarton.

This fixes an issue with negotiation of RTCP feedback.

Since we now make HTTP requests from addFilter, this makes
startup slightly faster.

This avoids throwing if the user changes their setting before
login.  Thanks to Jean-Jacques Sarton.

We used to initialise MediaPipe at worker start, which prevented
us from handling errors.  We now do it at filter init, and stop
the stream with an error message if initialisation fails.

We used to ignore errors in filter init, which could cause us
to send unblurred videos to the server.

We used blur the image then mask, which caused a halo around
the foreground.  We now mask then blur.

Thanks to Matohara Kenichiro.

This doesn't currently do anything useful, since we're running
tflite on the CPU, but might avoid bugs if we get GPU support.

This should free the underlying textures without waiting
for a GC to happen.

It doesn't work.