Feature: OG Social media cards

Not Original Gangsta, but ObjectGraph

Reason: images were showing on LinkedIn, but small.

blogex/lib/blogex/post.ex

@@ -28,6 +28,7 @@ defmodule Blogex.Post do
     :description,
     :date,
     :blog,
+    :image,
     tags: [],
     published: true
   ]
@@ -39,6 +40,7 @@ defmodule Blogex.Post do
           body: String.t(),
           description: String.t(),
           date: Date.t(),
+          image: String.t() | nil,
           tags: [String.t()],
           blog: atom(),
           published: boolean()

blogex/lib/blogex/seo.ex

@@ -3,11 +3,33 @@ defmodule Blogex.SEO do
   SEO helpers for generating meta tags and sitemaps.
   """
 
+  @doc """
+  Returns a map of meta tag attributes for a blog listing page.
+  Useful for setting OpenGraph and Twitter card tags on blog index pages.
+
+      <meta property="og:title" content={@meta.og_title} />
+  """
+  def meta_tags_for_blog(blog_module, base_url) do
+    url = "#{base_url}#{blog_module.base_path()}"
+
+    %{
+      title: blog_module.title(),
+      description: blog_module.description(),
+      og_title: blog_module.title(),
+      og_description: blog_module.description(),
+      og_type: "website",
+      og_url: url,
+      og_image: nil,
+      twitter_card: "summary"
+    }
+  end
+
   @doc """
   Returns a map of meta tag attributes for a post.
   Useful for setting OpenGraph and Twitter card tags in your layout.
 
       <meta property="og:title" content={@meta.og_title} />
+      <meta property="og:image" content={@meta.og_image} />
   """
   def meta_tags(post, base_url, blog_module) do
     url = "#{base_url}#{blog_module.base_path()}/#{post.id}"
@@ -19,6 +41,7 @@ defmodule Blogex.SEO do
       og_description: post.description,
       og_type: "article",
       og_url: url,
+      og_image: if(post.image, do: "#{base_url}#{post.image}", else: nil),
       article_published_time: Date.to_iso8601(post.date),
       article_author: post.author,
       article_tags: post.tags,