Add moderation warnings (#9519)

* Add moderation warnings

Replace individual routes for disabling, silencing, and suspending
a user, as well as the report update route, with a unified account
action controller that allows you to select an action (none,
disable, silence, suspend) as well as whether it should generate an
e-mail notification with optional custom text. That notification,
with the optional custom text, is saved as a warning.

Additionally, there are warning presets you can configure to save
time when performing the above.

* Use Account#local_username_and_domain

app/controllers/admin/account_actions_controller.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module Admin
+  class AccountActionsController < BaseController
+    before_action :set_account
+
+    def new
+      @account_action  = Admin::AccountAction.new(type: params[:type], report_id: params[:report_id], send_email_notification: true)
+      @warning_presets = AccountWarningPreset.all
+    end
+
+    def create
+      account_action                 = Admin::AccountAction.new(resource_params)
+      account_action.target_account  = @account
+      account_action.current_account = current_account
+
+      account_action.save!
+
+      if account_action.with_report?
+        redirect_to admin_report_path(account_action.report)
+      else
+        redirect_to admin_account_path(@account.id)
+      end
+    end
+
+    private
+
+    def set_account
+      @account = Account.find(params[:account_id])
+    end
+
+    def resource_params
+      params.require(:admin_account_action).permit(:type, :report_id, :warning_preset_id, :text, :send_email_notification)
+    end
+  end
+end