Replace PUT containers with POST containers

[roman-khimov]

Is your feature request related to a problem? Please describe.

I'm always frustrated when we're not following RFC 9110. The short definition of PUT is

Replace all current representations of the target resource with the request content.

The resource is containers, but we're far from replacing it here (since to GET containers is to obtain a list of them). We're just adding a new one.

Describe the solution you'd like

Make it a POST. Return 201 from it with a proper Location.

Describe alternatives you've considered

Keep as is, it works too. Well, we need to keep it anyway in deprecated fashion.

Additional context

https://www.rfc-editor.org/rfc/rfc9110.html