moq-pub: Avoid namespace conflict

[englishm]

We should either (or both):

• Allow users to specify a particular namespace as a command line argument
• Generate UUIDs as part of the namespaces (or maybe just as the default if nothing is specified) to avoid conflict

[englishm]

The current value is simply hardcoded here:

moq-rs/moq-pub/src/main.rs

Line 44 in 90818ac

media_runner.announce("quic.video/moq-pub-foo", media.source()).await?;

[zafergurel]

I got this.

[englishm]

Resolved by #66. Thanks @zafergurel!