Add size properties to EuiModal

[ryankeairns]

Fixes #1154

Adds height, maxHeight, width, and maxWidth to EuiModal.

The need for these properties occurrs in Canvas where users can search/filter table (workpad list) and grid (element types) content thus creating a situation where the height of theEuiModalBody content is dynamic.

To prevent the modal from being 'jumpy' (see https://github.com/elastic/kibana-canvas/issues/869 ) , we apply a height (in vh) to the modal. Related, since we're using vh, we don't want the modal to get too tall on large displays so we limit modal height using max-height.

🐉

[cchaos]

What happens if they set any of these to true?

[ryankeairns]

It has no impact. The boolean default was used here as a means for accepting and evaluating multiple PropTypes, allowing users to input a string or a number. The latter of which would have the recommended measurement applied to it.

There is similar logic in the flyout component that I was referring to.

[cchaos]

Sorry for my confusion, but why are we asking them to explicitly add these props when we just apply them to the style prop? Can't they just add them directly to style? It doesn't seem like this does anything more than the default style prop does?

[cchaos]

In the past we've added things like this because we were providing defaults with the option to set custom values. So when they passed a value, we would add a class and set a default value in CSS. This just passes it directly back to the style prop.

[ryankeairns]

The original discussion is here --> https://github.com/elastic/kibana-canvas/pull/1078#pullrequestreview-151207920

@cchaos I had similar feelings as I was building this out - realizing there are no defaults and that it just passes to style - but thought it was worth the convenience (and discussion) presuming this could be a fairly common scenario.

That said, maybe the default here is to set the height to 75vh and the prop is something like fixedHeight: true(Note: 75vh is the height set on euiModal_flex). Then we could leave the max-height style override up to the app/team implementing the modal.

[ryankeairns]

On second thought, I'm not sure a blanket 75vh is a good default. It seems the desired height would vary based upon each specific situation.

Perhaps a fixed height modal isn't a common enough use case to add these props, I suppose that is the core question here.