favgroups: don't allow favgroups to be named 'any' or 'none'.

'any' and 'none' are now reserved keywords for the favgroup: metatag.

Also add a fix script to rename existing favgroups.

script/fixes/108_fix_reserved_favgroups.rb

@@ -0,0 +1,15 @@
+#!/usr/bin/env ruby
+
+require_relative "base"
+
+with_confirmation do
+  FavoriteGroup.where(name: %w[any none]).find_each do |favgroup|
+    old_name = favgroup.name
+    favgroup.update!(name: "favgroup_#{favgroup.id}")
+
+    Dmail.create_automated(to: favgroup.creator, title: "Your favorite group has been renamed", body: <<~EOS)
+      Your favgroup ##{favgroup.id} has been renamed from "#{old_name}" to "#{favgroup.name}". "#{old_name}" is no longer an allowed favgroup name.
+      You can go "here":/favorite_groups/#{favgroup.id}/edit to change your favgroup's name to something else.
+    EOS
+  end
+end