In this commit, we create a new struct that houses the key derivation,
address management, and account management for a particular scope. A
scope consists of a (purpose, cointype) tuple. Additionally, each
ScopedKeyManager is able to generate internal/external addresses for a
specific *address type*. This make rescans easier as for each scope, we
know what type of output to look for within the chain.
The ScopedKeyManagers have two new primary methods that weren’t
previously present within the regular Manager:
* DeriveFromKeyPath
* NewRawAccount
These two methods allow callers a greater degree of control over the
way that accounted are created and addressed derived.
In this commit, we introduce the concept of scopes for individual key
managers. Each scope will lock down a key manager to a particular
purpose and coin type within the BIP0043 hierarchy. Each scope will
also have a set address type schema. This schema will be consulted when
creating addresses for a particular scoped key manager.
Finally, we introduce 3 new default scopes:
* BIP 44
* BIP 84
* BIP 49++ (BIP49 but uses p2wkh for change addresses)
