Add conversation model, <ostatus:conversation /> (#3016)

* Add <ostatus:conversation /> tag to Atom input/output

Only uses ref attribute (not href) because href would be
the alternate link that's always included also.

Creates new conversation for every non-reply status. Carries
over conversation for every reply. Keeps remote URIs verbatim,
generates local URIs on the fly like the rest of them.

* Fix conversation migration

* More spec coverage for status before_create

* Prevent n+1 query when generating Atom with the new conversations

* Improve code style

* Remove redundant local variable

1 files changed, 2 insertions, 0 deletions

diff --git a/spec/fabricators/conversation_fabricator.rb b/spec/fabricators/conversation_fabricator.rb
new file mode 100644
index 000000000..b4fadb46b
--- /dev/null
+++ b/spec/fabricators/conversation_fabricator.rb
@@ -0,0 +1,2 @@
+Fabricator(:conversation) do
+end