Adds factories for all middleware and a ConfigProvider

[weierophinney]

This patch accomplishes three things:

• It moves all middleware into a subnamespace, Zend\Expressive\Router\Middleware. This is done due to the large number of middleware now provided (six!), and the fact that each will have a factory.
• Adds factories for all provided middleware. In some cases, these depend on virtual services (e.g., response prototypes, callable factories). In those cases, per discussion in Suggestion for '<Dispatch|Route>Middleware::class' in 3.0alpha zend-expressive-skeleton#220, I've added package-level constants, and have the factories look for services named after those constant values, raising an exception if missing.
• Adds a ConfigProvider class that defines factory entries for each middleware, and registers the provider in the package.

[geerteltink]

Interesting solution to use the constants file. I thought you would use constants in the factories but this is a better solution. I only find the uppercase names ugly. But as they are constants you should, otherwise you still have confusion.

[michalbundyra]

LGTM 👍

[michalbundyra]

Why? Are lines too long?

[weierophinney]

Yes. :)

[weierophinney]

Interesting solution to use the constants file. I thought you would use constants in the factories but this is a better solution. I only find the uppercase names ugly. But as they are constants you should, otherwise you still have confusion.

Yeah, I prototyped originally with constants in the factories, and realized that was a poor solution when NOT using those factories. The PSR-1/2 and PSR-12 guides require constants be all-caps, underscore_separated, so I went with that style, and the values... well, seems like having them be equivalent to the constant name made as much sense as anything. I was happy with the end-result, particularly as these will essentially be inlined in the autoloader in production.