Subs to all topics, specify binary path, logic for all others as json

[dakota002]

Needed for nasa-gcn/gcn.nasa.gov/issues/1013

[lpsinger]

Before we can consider email alerts for topics that do not belong to GCN Classic, we need to be able to emulate the Kafka topic permissions for each user. That probably means being able to programmatically manage the Kafka topic permissions.

[lpsinger]

It's not safe to permit email subscriptions to any topic because not all users are supposed to have access to all topics.

[dakota002]

Should there be multiple consumers, like per group?
Should that be determined on the email subscriptions page? So that only the topics for the groups the user is part of are available?

Or would it be better to just exclude those that people shouldn't be subscribed to?

[lpsinger]

Fixed by #162.