Merge remote-tracking branch 'remotes/origin/usage' into usage
Merge branch 'master' into usage
payment: add index on payment_methods.external_key

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>
Merge branch 'usage' of github.com:killbill/killbill into usage
Merge branch 'master' into usage
Minor usage api chnage