clarify things around contact initiation
Hi! It it not really clear for me when reading the Specs when BHP is used. Basically it is only used currently in the Endpoint created in. I would add clarification to BHP, BRP and also generally tackle BHP+BRP in https://code.briarproject.org/briar/briar/-/wikis/A-Quick-Overview-of-the-Protocol-Stack .
The Key Agreement Protocol (https://chat.briarproject.org/briar/pl/rzro8mqxx7fz9x3cfmaejrkkbr ) is also currently never mentioned or specified.