Revert "Revert "Merge branch 'master' of https://github.com/discourse/discourse""

This reverts commit 20780a1eeed56b321daf18ee6bbfe681a51d1bf4.

* SECURITY: re-adds accidentally reverted commit:
  03d26cd6: ensure embed_url contains valid http(s) uri
* when the merge commit e62a85cf was reverted, git chose the 2660c2e2 parent to land on
  instead of the 03d26cd6 parent (which contains security fixes)

spec/components/email/processor_spec.rb

@@ -5,7 +5,7 @@ require "email/processor"
 
 describe Email::Processor do
   after do
-    Discourse.redis.flushall
+    Discourse.redis.flushdb
   end
 
   let(:from) { "foo@bar.com" }