Fix podcasts appearing in the "Writing" list

Before, podcast episodes appeared in both the "Writing" and "Podcasts"
lists. There was no need for this duplication, and we wanted to
highlight more of our content. We fixed the list only to include items
where we've marked `auto_social_share` as false.

[Trello](https://trello.com/c/2CIy3mOR)

Author: purinkle

lib/combined_rss_feed.rb

@@ -1,5 +1,9 @@
 require "rss_feed"
 
+class Feedjira::Parser::ITunesRSSItem
+  element "thoughtbot:auto_social_share", as: :auto_social_share
+end
+
 class CombinedRssFeed
   include Enumerable
 

lib/rss_feed.rb

@@ -4,6 +4,10 @@
 
 require "feed_item"
 
+class Feedjira::Parser::AtomEntry
+  element "thoughtbot:auto_social_share", as: :auto_social_share
+end
+
 class RssFeed
   include Enumerable
 
@@ -12,7 +16,7 @@ def initialize(url:)
   end
 
   def each
-    feed.entries.each do |entry|
+    feed.entries.reject { it.auto_social_share == "false" }.each do |entry|
       yield FeedItem.new(
         id: entry.id,
         title: entry.title,

spec/rss_feed_spec.rb

@@ -29,6 +29,58 @@
       )
     end
 
+    it "ignores entries we don't automatically share to social media" do
+      Excon.stub({}, {status: 200, body: <<~XML.chomp})
+        <?xml version="1.0" encoding="UTF-8"?>
+        <feed xmlns="http://www.w3.org/2005/Atom">
+          <title>TEST_FEED_TITLE</title>
+          <subtitle>TEST_SUBTITLE</subtitle>
+          <id>https://example.com/</id>
+          <link href="https://example.com/blog"/>
+          <link href="https://example.com/blog/feed.xml" rel="self"/>
+          <updated>2024-12-20T00:00:00+00:00</updated>
+          <author>
+            <name>TEST_NAME</name>
+          </author>
+          <entry>
+            <title>TEST_ENTRY_1</title>
+            <link rel="alternate" href="https://example.com/test-entry-1"/>
+            <author>
+              <name>TEST_AUTHOR</name>
+            </author>
+            <id>https://example.com/test-entry-1</id>
+            <published>2025-05-22T00:00:00+00:00</published>
+            <updated>2025-05-22T12:40:11Z</updated>
+            <content type="html">
+              <![CDATA[TEST_CONTENT]]>
+            </content>
+            <summary>TEST_SUMMARY</summary>
+            <thoughtbot:auto_social_share>false</thoughtbot:auto_social_share>
+          </entry>
+          <entry>
+            <title>TEST_ENTRY_2</title>
+            <link rel="alternate" href="https://example.com/test-entry-2"/>
+            <author>
+              <name>TEST_AUTHOR</name>
+            </author>
+            <id>https://example.com/test-entry-2</id>
+            <published>2025-05-29T00:00:00+00:00</published>
+            <updated>2025-05-29T12:40:11Z</updated>
+            <content type="html">
+              <![CDATA[TEST_CONTENT]]>
+            </content>
+            <summary>TEST_SUMMARY</summary>
+            <thoughtbot:auto_social_share>true</thoughtbot:auto_social_share>
+          </entry>
+        </feed>
+      XML
+      rss_feed = RssFeed.new url: "https://example.com/blog/feed.xml"
+
+      entries_titles = rss_feed.map(&:title)
+
+      expect(entries_titles).to contain_exactly "TEST_ENTRY_2"
+    end
+
     def atom_feed
       File.read("spec/fixtures/rss_feed.xml")
     end