fix location header lookup

Author: artemredkin

Diff for: Sources/AsyncHTTPClient/HTTPClient+HTTPCookie.swift

@@ -140,12 +140,8 @@ extension HTTPClient {
 }
 
 extension HTTPClient.Response {
-    var cookieHeaders: [HTTPHeaders.Element] {
-        return headers.filter { $0.name.lowercased() == "set-cookie" }
-    }
-
     /// List of HTTP cookies returned by the server.
     public var cookies: [HTTPClient.Cookie] {
-        return self.cookieHeaders.compactMap { HTTPClient.Cookie(header: $0.value, defaultDomain: self.host) }
+        return self.headers["set-cookie"].compactMap { HTTPClient.Cookie(header: $0, defaultDomain: self.host) }
     }
 }

Diff for: Sources/AsyncHTTPClient/HTTPHandler.swift

@@ -843,11 +843,11 @@ internal struct RedirectHandler<ResponseType> {
             return nil
         }
 
-        guard let location = headers.first(where: { $0.name == "Location" }) else {
+        guard let location = headers.first(name: "Location") else {
             return nil
         }
 
-        guard let url = URL(string: location.value, relativeTo: request.url) else {
+        guard let url = URL(string: location, relativeTo: request.url) else {
             return nil
         }
 

Diff for: Tests/AsyncHTTPClientTests/HTTPClientTestUtils.swift

@@ -269,7 +269,7 @@ internal final class HttpBinHandler: ChannelInboundHandler {
                 return
             case "/redirect/302":
                 var headers = HTTPHeaders()
-                headers.add(name: "Location", value: "/ok")
+                headers.add(name: "location", value: "/ok")
                 self.resps.append(HTTPResponseBuilder(status: .found, headers: headers))
                 return
             case "/redirect/https":