Find the route as soon as the URL is parsed

[The-EDev]

the TL;DR is that this PR makes it so that a request is routed as soon as the URL is parsed.

The long version is that it makes multiple changes to multiple parts of the framework, these changes are as follows:

• Common
  • replaced the tuples in the router with using routing_search_result and using routing_handle_result.
• Parser
  • Moves URL parameter handling to the on_url callback. (from the on_message_complete callback)
  • Adds new on_method callback that executes when the method is parsed
  • Replaces the to_request() method by immediately assigning any parsed data to a request object owned by the parser. (this is fine since the parser is owned by and exist for the lifetime of the HTTP connection)
  • Makes parser variables (except req) private.
  • Adds process_url() function to call a connection's handle_url(). (explained below)
• Connection
  • Alters the request object to be a reference the Parser's request object.
  • Adapts the functionality to the changes made in the Parser
  • Adds handle_url() function to call the router and behave according to the result. (i.e returning a response in case of a 404 or 405)
  • Adds a routing_handle_result property in order to check whether or not a route was found. (could be a good idea to replace with a boolean returned from handle_url() in the application)
• Router
  • Improves the way a Trie is printed out. (I needed that for debugging)
  • Splits the handle() method into 2 separate methods, one that deals with only finding a route and another that does the actual handling.

The other changes are either documentation related or only there to adapt to the changes above.

This PR closes #493 and make an implementation for #397 possible.

[crow-clang-format]

--- include/crow/routing.h	(before formatting)
+++ include/crow/routing.h	(after formatting)
@@ -1626,7 +1626,7 @@
             else // Every request that isn't a HEAD or OPTIONS request
             {
                 search_result = per_methods_[static_cast<int>(method_actual)].trie.find(req.url);
-// TODO(EDev): maybe ending the else here would allow the requests coming from above (after removing the return statement) to be checked on whether they actually point to a route
+                // TODO(EDev): maybe ending the else here would allow the requests coming from above (after removing the return statement) to be checked on whether they actually point to a route
                 if (!std::get<0>(search_result))
                 {
                     for (auto& per_method : per_methods_)

[andrew-guz]

After that changes, CORS is not working for WebKit browser (for example, Epiphany). Can not parse request...