Not losing related peers info on restart

[pgmemk]

Problem

In this version of multi-hyperbee the related peers are saved only in memory.
That means that if the device restarts there is no info for restoring the relationship.

Solution

• Save the list of related peers as a manifest in store hyperbee (multi-hyperbee has local store, local diff and many remote diff replicas.
• Save the name of this key in the Header (first block in hyperbee or any other hyper data structure)
• Use this key to save/update the manifest every time the new peer is added/removed.

Discuss if this works for other multi-feed structures

dat-ecosystem/comm-comm#134

[pgmemk]

Implemented as planned.