Update in-memory storage implementation to parse full address strings in
saveIdentity. Update usage of saveIdentity, passing in the full address string.
Reflect whether a saveIdentity operation reflects a replacement of an existing
key or not. The return value can be used by the caller to decide whether they
should clear sessions for the recipient.
Pass in a direction to isTrusted, based on constants defined by the storage
implementation. These values allow the trust store to determine whether a given
key is trusted, given the directional context.
This was mostly used internally by SessionRecord to flag the lack of an
open session, but that can be replaced with an actual check for an open
session.
This is redundant to the identity key store, and only used to check
internal consistency between sessions and the 'current' remote identity,
though there's no particular reason we can't keep sessions from previous
identity keys.
