fix NullPointerException for empty map in CaptchaProperties

Author: tobiasholler

captchaservice-backend/src/main/java/de/muenchen/captchaservice/configuration/captcha/CaptchaProperties.java

@@ -12,7 +12,7 @@ public record CaptchaProperties(@NotBlank String hmacKey, long ttlSeconds, Map<S
     public CaptchaProperties(final String hmacKey, final long ttlSeconds, final Map<String, CaptchaSite> sites, final long sourceAddressWindowSeconds) {
         this.hmacKey = hmacKey;
         this.ttlSeconds = ttlSeconds;
-        this.sites = Map.copyOf(sites);
+        this.sites = sites != null ? Map.copyOf(sites) : Map.of();
         this.sourceAddressWindowSeconds = sourceAddressWindowSeconds;
     }
 }

captchaservice-backend/src/main/java/de/muenchen/captchaservice/configuration/captcha/CaptchaSite.java

@@ -1,8 +1,10 @@
 package de.muenchen.captchaservice.configuration.captcha;
 
+import jakarta.validation.constraints.NotNull;
+
 import java.util.List;
 
-public record CaptchaSite(String siteKey, String secret, List<DifficultyItem> difficultyMap) {
+public record CaptchaSite(String siteKey, String secret, @NotNull List<DifficultyItem> difficultyMap) {
     public CaptchaSite(final String siteKey, final String secret, final List<DifficultyItem> difficultyMap) {
         this.siteKey = siteKey;
         this.secret = secret;

captchaservice-backend/src/main/resources/application.yml

@@ -55,5 +55,5 @@ info:
 
 captcha:
   hmac-key: null
-  sites: []
+  sites: {}
   ttl-seconds: 1200