Allow empty header values

Author: jimmy-park

httplib.h

@@ -4115,7 +4115,7 @@ inline bool parse_header(const char *beg, const char *end, T fn) {
     p++;
   }
 
-  if (p < end) {
+  if (p <= end) {
     auto key_len = key_end - beg;
     if (!key_len) { return false; }
 

test/test.cc

@@ -4923,6 +4923,13 @@ TEST(ServerRequestParsingTest, InvalidFieldValueContains_CR_LF_NUL) {
   EXPECT_EQ("HTTP/1.1 400 Bad Request", out.substr(0, 24));
 }
 
+TEST(ServerRequestParsingTest, EmptyFieldValue) {
+  std::string out;
+  
+  test_raw_request("GET /header_field_value_check HTTP/1.1\r\nTest: \r\n", &out);
+  EXPECT_EQ("HTTP/1.1 200 OK", out.substr(0, 15));
+}
+
 TEST(ServerStopTest, StopServerWithChunkedTransmission) {
   Server svr;