Marshmallow warnings

[zedrdave]

As of the current version of Marshmallow, there are a number of compatibility warnings (mainly caused by the use of ordered in the Pagination schema).

I believe the current dev version of flask-smorest fixes this, but it seems like it's been stuck in limbo for a while. Would you consider releasing a new version with these fixes?

[lafrech]

Yup. I was waiting for marshmallow 4 to ship, but this seems to take a little time.

I just tried to release 0.46.0 with the compatibility fixes for latest marshmallow 3.x but got a CI issue. I'll try to carve out some time soonish to fix this and investigate #762.

[lafrech]

The CI issue was transient. 0.46.0 is out so the warnings issue should be solved.

BTW, marshmallow 4 just shipped! I shall publish a new flask-smorest version soon. Changes are minimal (and only in tests).