[1.0] Use a union type for an array linked node field pointing to heterogenous types

[KyleAMathews]

No description provided.

[KyleAMathews]

Hit need for this while working on the contentful source plugin as you can have an array of linked mixed types but (crucially) where the order is important. E.g. pageContent is an array of fields some fields have an image and text and others are just text. I think converting this into a union type makes the most sense.

So I think I changed my mind from #928 (comment) :-)

An array/list of mixed things just makes sense from a data modeling perspective sometimes so we need to support it.

@jquense thoughts here?

[gatsbybot]

Deploy preview ready!

Built with commit 49052d7

https://deploy-preview-1211--using-drupal.netlify.com

[gatsbybot]

Deploy preview ready!

Built with commit 49052d7

https://deploy-preview-1211--gatsbyjs.netlify.com

[gatsbybot]

Deploy preview ready!

Built with commit 49052d7

https://deploy-preview-1211--gatsbygram.netlify.com

[KyleAMathews]

Gonna merge now as but feel free to comment so we can tweak things before next beta.

[KyleAMathews]

@0x80 do you have anything like this with your use of Contentful?

[0x80]

@KyleAMathews No, I don't have a use-case for that currently. All my arrays are of a single type.