Add optional title to front matter

lib/micropub/post.rb

@@ -1,4 +1,5 @@
 require "date"
+require "yaml"
 require "kramdown"
 
 module Micropub
@@ -67,13 +68,18 @@ module Micropub
       end
     end
 
+    def post_frontmatter
+      {
+        "title" => title,
+        "date" => published.rfc3339,
+        "layout" => "micropost",
+        "categories" => categories,
+      }.compact.to_yaml
+    end
+
     def post_content
       <<~POST
-      ---
+      #{post_frontmatter.strip}
-      date: '#{published.rfc3339}'
-      layout: micropost
-      categories:
-      #{categories.map { |category| "- #{category}\n" }.join.strip}
       ---
 
       #{content}

test/lib/micropub/models/post_test.rb

@@ -205,5 +205,28 @@ describe Micropub::Post do
         Hallo, Earth!
       POST
     end
+
+    it "returns a post formatted for hugo with a title" do
+      post = Micropub::Post.new(
+        "title" => "Welcome!",
+        "content" => "Hallo, Earth!",
+        "published" => "2019-11-12",
+        "category" => ["one", "two", "three"],
+      )
+
+      _(post.post_content).must_equal <<~POST
+        ---
+        title: Welcome!
+        date: '2019-11-12T00:00:00+00:00'
+        layout: micropost
+        categories:
+        - one
+        - two
+        - three
+        ---
+
+        Hallo, Earth!
+      POST
+    end
   end
 end