Add posts, tags, tagging, to database. Create references to align with new DB model. Add image of mermaid template model.

app/models/post.rb

@@ -0,0 +1,6 @@
+class Post < ApplicationRecord
+  belongs_to :user
+  belongs_to :image
+  has_many :taggings, as: :taggable
+  has_many :tags, through: :taggings
+end