display existing fields while editing posts

Pull the post data including tags from the db. Assign them instance variables.

Put that data in the value fields of the post edit form.
add logic and routing for displaying a single post

Add a url_title field to the posts table migration for an html and SEO safe blog post url.

Add a method in the post model to automatically generate the snake_case url from the post's title. This is yet to be called anywhere. This can be called as soon as a post is entered into the database, since the title is a required field.

Add the routing and logic to access that new field in the controller. Route to a display_post erb.