[Feature]: Recipient and sender must send message each before starting voice/video call

[mjovanc]

Description of feature request

Don't open up channel for voice or video call unless the recipient has responded to the first initial message so if a Hugin address is shared to another person, people can not just call up persons.

Why is this needed

Let's say someone gets my Hugin address or shared to a lot of people, they can just call me directly without me "approving" it. So to make this a little safer, it could be good to have a criteria that both the recipient and sender should send a message initially. 

I'm not sure if that's the case currently, or just one message first.

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