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/warning_presets_controller.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+module Admin
+  class WarningPresetsController < BaseController
+    before_action :set_warning_preset, except: [:index, :create]
+
+    def index
+      authorize :account_warning_preset, :index?
+
+      @warning_presets = AccountWarningPreset.all
+      @warning_preset  = AccountWarningPreset.new
+    end
+
+    def create
+      authorize :account_warning_preset, :create?
+
+      @warning_preset = AccountWarningPreset.new(warning_preset_params)
+
+      if @warning_preset.save
+        redirect_to admin_warning_presets_path
+      else
+        @warning_presets = AccountWarningPreset.all
+        render :index
+      end
+    end
+
+    def edit
+      authorize @warning_preset, :update?
+    end
+
+    def update
+      authorize @warning_preset, :update?
+
+      if @warning_preset.update(warning_preset_params)
+        redirect_to admin_warning_presets_path
+      else
+        render :edit
+      end
+    end
+
+    def destroy
+      authorize @warning_preset, :destroy?
+
+      @warning_preset.destroy!
+      redirect_to admin_warning_presets_path
+    end
+
+    private
+
+    def set_warning_preset
+      @warning_preset = AccountWarningPreset.find(params[:id])
+    end
+
+    def warning_preset_params
+      params.require(:account_warning_preset).permit(:text)
+    end
+  end
+end