improv: #5 handle the request and return a response (useful for tests)

src/handlers/request.rs

@@ -122,7 +122,7 @@ impl HTTPStartLine {
         HTTP_VERSION_REGEX.is_match(version)
     }
 
-    fn is_valid(&self) -> bool {
+    pub fn is_valid(&self) -> bool {
         return self.method != "" && self.target != "";
     }
 }
@@ -234,7 +234,7 @@ impl HTTPRequest {
         }
     }
 
-    fn is_valid(&self) -> bool {
+    pub fn is_valid(&self) -> bool {
         return self.start_line.is_valid();
     }
 }