Fix test configs: provide all required schema fields

Schema validation was failing because the new optional config fields
(protected_paths, challenge_type, pow_difficulty) weren't provided in
test configs. While these fields have defaults in the code, the schema
validator requires them to be present.

Added all three fields to every test setup() method with appropriate
default values.

tests/ddos_protection_challenge.lua

@@ -56,7 +56,10 @@ function TestDDoSProtectionChallenge:setup()
         token_duration = 86400,
         cookie_name = 'aproxy_token',
         shared_dict_bans = 'aproxy_bans',
-        shared_dict_tokens = 'aproxy_tokens'
+        shared_dict_tokens = 'aproxy_tokens',
+        protected_paths = {},
+        challenge_type = 'button',
+        pow_difficulty = 4
     })
 end
 
@@ -233,7 +236,9 @@ function TestDDoSProtectionChallengePaths:setup()
         cookie_name = 'aproxy_token',
         shared_dict_bans = 'aproxy_bans',
         shared_dict_tokens = 'aproxy_tokens',
-        protected_paths = {'/api/.*', '/search'}
+        protected_paths = {'/api/.*', '/search'},
+        challenge_type = 'button',
+        pow_difficulty = 4
     })
 end
 
@@ -380,7 +385,9 @@ function TestDDoSProtectionChallengeQuestion:setup()
         cookie_name = 'aproxy_token',
         shared_dict_bans = 'aproxy_bans',
         shared_dict_tokens = 'aproxy_tokens',
-        challenge_type = 'question'
+        protected_paths = {},
+        challenge_type = 'question',
+        pow_difficulty = 4
     })
 end
 
@@ -495,6 +502,7 @@ function TestDDoSProtectionChallengePow:setup()
         cookie_name = 'aproxy_token',
         shared_dict_bans = 'aproxy_bans',
         shared_dict_tokens = 'aproxy_tokens',
+        protected_paths = {},
         challenge_type = 'pow',
         pow_difficulty = 4
     })