Add LndHub db/models, and quick stats for admin views

app/models/user.rb

@@ -5,6 +5,11 @@ class User < ApplicationRecord
   has_many :invitations, dependent: :destroy
   has_many :donations, dependent: :nullify
 
+  has_one  :lndhub_user, class_name: "LndhubUser", inverse_of: "user",
+                         primary_key: "ln_account", foreign_key: "login"
+
+  has_many :accounts, through: :lndhub_user
+
   validates_uniqueness_of :cn
   validates_length_of :cn, :minimum => 3
   validates_uniqueness_of :email