Refactor micropub specific things out to a slice

slices/micropub/actions/webmentions/create.rb

@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+module Micropub
+  module Actions
+    module Webmentions
+      class Create < Adamantium::Action
+        include Deps["repos.webmentions_repo",
+          "repos.post_repo",
+          webmention_parser: "param_parser.webmention"
+                ]
+
+        def handle(req, res)
+          webmention = webmention_parser.call(params: req.params)
+          case webmention
+          in Success[:reply, reply]
+            slug = req.params[:"in-reply-to"].split("/").last
+            post = post_repo.fetch!(slug)
+
+            reply[:post_id] = post.id
+
+            webmentions_repo.create(reply)
+            res.status = 201
+          in Failure(:invalid_request)
+            res.status = 429
+          in Failure(:not_implemented)
+            res.status = 429
+          end
+        end
+      end
+    end
+  end
+end