Allow adding of syndication sources after a post is created

slices/admin/commands/posts/add_syndication_source.rb

@@ -0,0 +1,22 @@
+require "readability"
+require "down"
+
+module Admin
+  module Commands
+    module Posts
+      class AddSyndicationSource
+        include Dry::Monads[:result]
+        include Deps["repos.post_repo"]
+
+        def call(post_id:, source_name:, source_url:)
+          post = post_repo.find(id: post_id)
+          syndication_sources = post[:syndication_sources]
+          updated_syndication_sources = syndication_sources.merge(source_name => source_url)
+
+          post_repo.update(post_id, syndication_sources: updated_syndication_sources)
+          Success()
+        end
+      end
+    end
+  end
+end