getSignedUrl doesn't call callback for putObject operation

[ScottyMJacobson]

getObject works as expected, but putObject looks like it's still stubbed out without a fake implementation (one that would call the callback or work as a promisified)

mock-aws-s3/lib/mock.js

Line 621 in 6b5aa02

case 'putObject':

I think the solution would be just to add callback(null, url) on like 625? Would need to look more at the spec for getSignedUrl to make sure the dummy url would work for both

[muhammadfaizan]

@ScottyMJacobson same issue, guess we need to send a PR