Explain dynamic attributes support

[alexbudarov]

As far as I was told, REST API supports dynamic attributes.
You just have to start attribute names with plus, e.g. "+vatNumber".

But manual has zero mentions of the word "dynamic".

[alexbudarov]

e.g. see this forum question:
https://www.cuba-platform.com/discuss/t/how-to-add-a-dynamic-attribute-through-rest-api-add-on/11649

[alexbudarov]

another question: https://www.cuba-platform.com/discuss/t/is-it-posssible-to-get-dynamicattributes-of-a-entity-through-rest-api-metadata-endpoint-baseurl-metadata-entities/11738