Add placeholder support for prefix and host

[sstok]

To add support for placeholders there a number of risks. A negative lookahead regex pattern must only be used when there are sections that match, else ^/(?!(user)/) is going to fail with /user/ in the backend section (with it's host).

Regex parsing is a complex and error prone process, and needs to as good as possible. This however means that complex patterns are not supported, only simple ones with a single-level grouping (en_(us|uk), (en|nl)) and no look around placeholders replaces ((something)_\1).

Some idea's and notes for later:

• Add support for simple regexes patterns, no nested groups or complex stuff
• strip placeholders and compare result, same means the host-group (first stage, stop if not equal)
• apply placeholder regexes, and compare result, same means same host-group (second stage, continue if not match. return true when equal)
• Use the compiled route for information extraction.
• Convert character-class to an array, sort, and implode (to get same matching groups) (final check, this ensures a same order for same matching regex).

[sstok]

Instead of making this to feature envy, it's possible to add support for {_locale} and host requirements without to much effort.

[sstok]

OK, the good news is. It possible, for host at least. And I actually managed to do this 👍 Using icomefromthenet/reverse-regex you can create results based on a regex and then check if these outcomes match the other patterns, making host groups instead of checking hosts statically.

Adding this for the prefix is going to kill me 💀 The amount of possible outcomes is to complex for what anyone would ever use, eg. you have to require anyone who uses placeholders to provide a regex that doesn't conflict with others (defeating the purpose of this bundle) or you can't use complex expressions.

Instead for the prefix I'm thinking of a | to allow more then one static prefix, these can still be validated and allow for more complex prefixes like backend|admin|bop.

[sstok]

I have an idea how to solve this, but it's going to be big BC break. Basically the following: Remove support regex in host and prefix, it's still possible to use multiple values (admin|backoffice) but no advanced regexp.

This makes the configuration more predictable and makes adding features much easier.

[sstok]

Resolved by #18