Pass context to components through mount

[matthewmcgarvey]

Purpose

Related to #1152

Description

Instead of implementing mount_defaults the main code that we want passed down into components without being asked for is the context. This adds it to be passed in just like view is.

[stephendolan]

@matthewmcgarvey This is awesome, and if we can extend @context to hold more than just HTTP::Server::Context (like current_site or current_user), then I think the need for mount_defaults goes away entirely!

I'm having trouble visualizing when I'd hit the scenario you describe here:

or set it with 'context(@context)' before rendering.

What would that look like in an app to render a component without mount?

[jwoertink]

That's funny, I had the same thought just the other day! Really, this is the big one. Anything else like current_user or current_site can still be as needed. This was really the only annoying one. I dig it!

[matthewmcgarvey]

On my phone so I can't link to the specific lines but at the bottom of this file where components can be provided also needs to pass in the context https://www.github.com/luckyframework/lucky/tree/master/src/lucky/renderable.cr

[stephendolan]

Ah, right!

[matthewmcgarvey]

@jwoertink @stephendolan You approved when it was a draft, is this good to merge now?

[jwoertink]

Yup. Looks good to me

[stephendolan]

Likewise! I don't see any downsides to getting this merged.