Add debug logging to diagnose token validation failures

Added debug logging to see what's happening with cookie header
parsing in the failing token validation tests. This will help
identify whether:
- ngx.req.get_headers() is returning the expected headers
- The Cookie header is being found (case sensitivity check)
- The token is being extracted correctly
- The token is found in the shared dict

Also added ngx log level constants (DEBUG, INFO, WARN, ERR) to
the test framework since the module uses them.

scripts/ddos_protection_challenge.lua

@@ -539,12 +539,19 @@ local function challengeCallback(cfg, state)
 
     -- Check for valid token cookie
     local headers = ngx.req.get_headers()
+    ngx.log(ngx.DEBUG, "DEBUG: headers type = " .. type(headers))
+    if headers then
+        ngx.log(ngx.DEBUG, "DEBUG: headers.Cookie = " .. tostring(headers["Cookie"]))
+        ngx.log(ngx.DEBUG, "DEBUG: headers.cookie = " .. tostring(headers["cookie"]))
+    end
     local cookie_header = headers["Cookie"]
     local token = getCookieValue(cookie_header, cfg.cookie_name)
+    ngx.log(ngx.DEBUG, "DEBUG: token extracted = " .. tostring(token))
 
     if token then
         -- Verify token is still valid in shared dict
         local is_valid = state.tokens_dict:get(token)
+        ngx.log(ngx.DEBUG, "DEBUG: token is_valid = " .. tostring(is_valid))
         if is_valid then
             -- Token is valid, allow request through
             return nil

test.lua

@@ -20,6 +20,12 @@ function createNgx()
         print(msg)
     end
 
+    -- Log level constants
+    ngx.DEBUG = 7
+    ngx.INFO = 6
+    ngx.WARN = 4
+    ngx.ERR = 3
+
     -- only hold data here
     ngx.var = {}