Redirect to url with trailing slash, WITHOUT the protocol and host.

Crow does not know the correct protocol when behind a reverse proxy.
So instead, simply redirect to the same url and add a trailing slash.

Note, it is now valid for the "Location" header field to be relative.
From wikipedia:
An obsolete version of the HTTP 1.1 specifications (IETF RFC 2616)
required a complete absolute URI for redirection.
The IETF HTTP working group found that the most popular web browsers
tolerate the passing of a relative URL[3] and, consequently, the updated
HTTP 1.1 specifications (IETF RFC 7231) relaxed the original constraint,
allowing the use of relative URLs in Location headers.

include/crow/http_connection.h

@@ -258,18 +258,6 @@ namespace crow
                 }
             }
 #endif
-            //if there is a redirection with a partial URL, treat the URL as a route.
-            std::string location = res.get_header_value("Location");
-            if (!location.empty() && location.find("://", 0) == std::string::npos)
-            {
-#ifdef CROW_ENABLE_SSL
-                if (handler_->ssl_used())
-                    location.insert(0, "https://" + req_.get_header_value("Host"));
-                else
-#endif
-                    location.insert(0, "http://" + req_.get_header_value("Host"));
-                res.set_header("location", location);
-            }
 
             prepare_buffers();
 

include/crow/routing.h

@@ -1462,16 +1462,7 @@ namespace crow // NOTE: Already documented in "crow/app.h"
             {
                 CROW_LOG_INFO << "Redirecting to a url with trailing slash: " << req.url;
                 res = response(301);
-
-                // TODO(ipkn) absolute url building
-                if (req.get_header_value("Host").empty())
-                {
-                    res.add_header("Location", req.url + "/");
-                }
-                else
-                {
-                    res.add_header("Location", (using_ssl ? "https://" : "http://") + req.get_header_value("Host") + req.url + "/");
-                }
+                res.add_header("Location", req.url + "/");
                 res.end();
                 return;
             }
@@ -1710,16 +1701,7 @@ namespace crow // NOTE: Already documented in "crow/app.h"
             {
                 CROW_LOG_INFO << "Redirecting to a url with trailing slash: " << req.url;
                 res = response(301);
-
-                // TODO(ipkn) absolute url building
-                if (req.get_header_value("Host").empty())
-                {
-                    res.add_header("Location", req.url + "/");
-                }
-                else
-                {
-                    res.add_header("Location", (using_ssl ? "https://" : "http://") + req.get_header_value("Host") + req.url + "/");
-                }
+                res.add_header("Location", req.url + "/");
                 res.end();
                 return;
             }