remove node='mix' for channel discovery; + ensure conference is type mix, and note registration requirements;
The MIX service then MUST return its identity and the features it supports, which MUST include the 'urn:xmpp:mix:core:0' feature, and the identity MUST have a category of 'conference' and a type of 'text', as shown in the following example:
+The MIX service then MUST return its identity and the features it supports, which MUST include the 'urn:xmpp:mix:core:0' feature, and the identity MUST have a category of 'conference' and a type of 'mix', as shown in the following example:
The urn:xmpp:mix namespace needs to be registered.
+The conference type 'mix' needs to be registered.