Explore using JetBrains' ArrayShape attribute

[Crell]

Detailed description

Can we leverage this somehow, especially for deserializing objects embedded in arrays?

https://github.com/JetBrains/phpstorm-attributes#arrayshape

Context

Some folks are working with really bad APIs...

Possible implementation

Probably ArrayShape would have to be a sub-attribute of DictionaryField, and get folded into that. Somehow.