Handling extension of verbs in MOQT

[gloinul]

The CAT 4 MoQT token will need to handle the extensibility of the MOQT protocol. As this is still being discussed in the WG it might be a little early to lock the solution down. But lets start discussing how to handle the part that effects the tokens.

So although it may be that the core verbs will be non-extensible under a particular moqt version, identified like this under a particular ALPN identifer. We need to discuss both extension being defined as part of the MOQT setup process. It is also a question of how to handle future ALPN versions of MOQT where additional or other verbs could be defined. To make the CAT token as stable as possible I believe that it would be good to ensure that new verbs that would require authorization can be registered relatively simple and that be expressed by the token.