isEqual = (a, b) => {
  return a.id === b.id &&
    a.hash === b.hash &&
    a.type === b.type &&
    a.publicKey === b.publicKey &&
    a.signatures.id === b.signatures.id &&
    a.signatures.publicKey === b.signatures.publicKey
}
Evaluates whether two identities are equal.
@param {Identity} a First identity.
@param {Identity} b Second identity.
@return {boolean} True if identity a and b are equal, false otherwise.
@static
@private