API v1 financial_transactions endpoints (#627)

app/controllers/api/v1/user/financial_transactions_controller.rb

@@ -0,0 +1,21 @@
+class Api::V1::User::FinancialTransactionsController < Api::V1::BaseController
+  include Concerns::CollectionScope
+
+  before_action ->{ doorkeeper_authorize! 'finance:user' }
+  before_action :require_ordergroup
+
+  def index
+    render_collection search_scope
+  end
+
+  def show
+    render json: scope.find(params.require(:id))
+  end
+
+  private
+
+  def scope
+    current_ordergroup.financial_transactions.includes(:user)
+  end
+
+end