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

This reverts commit 20780a1eee.

* 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/discourse_redis_spec.rb

@@ -21,11 +21,11 @@ describe DiscourseRedis do
     let(:raw_redis) { Redis.new(DiscourseRedis.config) }
 
     before do
-      raw_redis.flushall
+      raw_redis.flushdb
     end
 
     after do
-      raw_redis.flushall
+      raw_redis.flushdb
     end
 
     describe 'when namespace is enabled' do