Account:: namespace simplifications and cleanup (#2110)

* Flatten Holding model

* Flatten balance model

* Entries domain renames

* Fix valuations reference

* Fix trades stream

* Fix brakeman warnings

* Fix tests

* Replace existing entryable type references in DB

app/controllers/holdings_controller.rb

@@ -0,0 +1,29 @@
+class HoldingsController < ApplicationController
+  before_action :set_holding, only: %i[show destroy]
+
+  def index
+    @account = Current.family.accounts.find(params[:account_id])
+  end
+
+  def show
+  end
+
+  def destroy
+    if @holding.account.plaid_account_id.present?
+      flash[:alert] = "You cannot delete this holding"
+    else
+      @holding.destroy_holding_and_entries!
+      flash[:notice] = t(".success")
+    end
+
+    respond_to do |format|
+      format.html { redirect_back_or_to account_path(@holding.account) }
+      format.turbo_stream { render turbo_stream: turbo_stream.action(:redirect, account_path(@holding.account)) }
+    end
+  end
+
+  private
+    def set_holding
+      @holding = Current.family.holdings.find(params[:id])
+    end
+end