refine url normalization

Before, the entire url was being lowercased, which mutilates various case-sensitive parts.
Now, only the host gets lowercased, and the test verify that the userinfo, path, and query parts preserve their original case.

transport/url.go

@@ -22,13 +22,18 @@ func ParseURL(urlStr string) (*url.URL, error) {
 }
 
 func NormalizeURL(input string) (string, error) {
-	parsed, err := ParseURL(strings.ToLower(input))
+	parsed, err := ParseURL(input)
 	if err != nil {
 		return "", err
 	}
 
+	// lowercase host
+	parsed.Host = strings.ToLower(parsed.Host)
+
 	host := parsed.Hostname()
 	port := parsed.Port()
+
+	// strip default ports
 	if (parsed.Scheme == "wss" && port == "443") ||
 		(parsed.Scheme == "ws" && port == "80") {
 		parsed.Host = host

transport/url_test.go

@@ -142,6 +142,22 @@ func TestNormalizeURL(t *testing.T) {
 			input:    "wss://relay.example.com/nostr",
 			expected: "wss://relay.example.com/nostr",
 		},
+		{
+			name:     "lowercase scheme+host, preserve path case",
+			input:    "Wss://Relay.Example.Com/Nostr",
+			expected: "wss://relay.example.com/Nostr",
+		},
+		{
+			name:  "preserve user info",
+			input: "wss://user:P@ssWord@relay.example.com",
+			// String() cannot output a raw `@` so `%40` is expected
+			expected: "wss://user:P%40ssWord@relay.example.com",
+		},
+		{
+			name:     "preserve query",
+			input:    "Wss://relay.example.com?field=Value",
+			expected: "wss://relay.example.com?field=Value",
+		},
 		{
 			name:     "no change needed",
 			input:    "wss://relay.example.com",