Budgeting V1 (#1609)

* Budgeting V1

* Basic UI template

* Fully scaffolded budgeting v1

* Basic working budget

* Finalize donut chart for budgets

* Allow categorization of loan payments for budget

* Include loan payments in incomes_and_expenses scope

* Add budget allocations progress

* Empty states

* Clean up budget methods

* Category aggregation queries

* Handle overage scenarios in form

* Finalize budget donut chart controller

* Passing tests

* Fix allocation naming

* Add income category migration

* Native support for uncategorized budget category

* Formatting

* Fix subcategory sort order, padding

* Fix calculation for category rollups in budget

app/models/budgeting_stats.rb

@@ -0,0 +1,29 @@
+class BudgetingStats
+  attr_reader :family
+
+  def initialize(family)
+    @family = family
+  end
+
+  def avg_monthly_income
+    income_expense_totals_query(Account::Entry.incomes)
+  end
+
+  def avg_monthly_expenses
+    income_expense_totals_query(Account::Entry.expenses)
+  end
+
+  private
+    def income_expense_totals_query(type_scope)
+      monthly_totals = family.entries
+                        .merge(type_scope)
+                        .select("SUM(account_entries.amount) as total")
+                        .group(Arel.sql("date_trunc('month', account_entries.date)"))
+
+      result = Family.select("AVG(mt.total)")
+                     .from(monthly_totals, :mt)
+                     .pick("AVG(mt.total)")
+
+      result
+    end
+end