add creature and base rp_world

app/models/rp_world.rb

@@ -0,0 +1,9 @@
+class RpWorld < ApplicationRecord
+  belongs_to :user
+  alias_attribute :owner, :user
+  has_many :wow_character_play_rp_worlds, dependent: :destroy
+  has_many :wow_characters, through: :wow_character_play_rp_worlds
+  alias_attribute :members, :wow_characters
+
+  validates :name, presence: true
+end