Introduce Ostatus name space (#4164)

* Wrap methods of ProcessFeedService::ProcessEntry in classes

This is a change same with 425acecfdb, except
that it has the following changes:

* Revert irrelevant change in find_or_create_conversation
* Fix error handling for RemoteActivity

* Introduce Ostatus name space

app/lib/ostatus/activity/share.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+class Ostatus::Activity::Share < Ostatus::Activity::Creation
+  def perform
+    return if reblog.nil?
+
+    status, just_created = super
+    NotifyService.new.call(reblog.account, status) if reblog.account.local? && just_created
+    status
+  end
+
+  def object
+    @xml.at_xpath('.//activity:object', activity: TagManager::AS_XMLNS)
+  end
+
+  private
+
+  def reblog
+    return @reblog if defined? @reblog
+
+    original_status = Ostatus::Activity::Remote.new(object).perform
+    return if original_status.nil?
+
+    @reblog = original_status.reblog? ? original_status.reblog : original_status
+  end
+end