FEATURE: Add rake task to disable secure media (#8669)

* Add a rake task to disable secure media. This sets all uploads to `secure: false`, changes the upload ACL to public, and rebakes all the posts using the uploads to make sure they point to the correct URLs. This is in a transaction for each upload with the upload being updated the last step, so if the task fails it can be resumed.
* Also allow viewing media via the secure url if secure media is disabled, redirecting to the normal CDN url, because otherwise media links will be broken while we go and rebake all the posts + update ACLs

spec/requests/uploads_controller_spec.rb

@@ -431,6 +431,23 @@ describe UploadsController do
         result = JSON.parse(response.body)
         expect(result[0]["url"]).to match("secure-media-uploads")
       end
+
+      context "when secure media is disabled" do
+        before do
+          SiteSetting.secure_media = false
+        end
+
+        it "should redirect to the regular show route" do
+          secure_url = upload.url.sub(SiteSetting.Upload.absolute_base_url, "/secure-media-uploads")
+          sign_in(user)
+          stub_request(:head, "https://#{SiteSetting.s3_upload_bucket}.s3.amazonaws.com/")
+
+          get secure_url
+
+          expect(response.status).to eq(302)
+          expect(response.redirect_url).to eq(Discourse.store.cdn_url(upload.url))
+        end
+      end
     end
   end