Generate a Hash key when the library is started

[githengi]

• Generate a Hash key for each device when the library is starting up .

• The Hash key will be generated once during the life cycle of the app, if does not exist

• After authentication and authorization on both devices the sender will send their Hash key to the receiver.

• The receiver will maintain a record of sending devices and their hash key in a SQLite table p2p_hash_keys.

• If a sender sends a different Hash key than the previous known hashkey, the records in p2p_received_history for that device are deleted.

This means that all data in the sender should be sent to the receiver.