fix(core): add secrets cache

closes #1679

core/src/main/java/io/kestra/core/secret/SecretService.java

@@ -4,14 +4,31 @@
 import jakarta.inject.Singleton;
 
 import java.util.Base64;
+import java.util.HashMap;
+import java.util.Map;
 import java.util.Optional;
 
 @Singleton
 public class SecretService {
+    private Map<String, String> decodedSecrets;
+
     public String findSecret(String key) throws IllegalVariableEvaluationException {
-        String environmentVariable = Optional.ofNullable(System.getenv("SECRETS_" + key.toUpperCase()))
-            .orElseThrow(() -> new IllegalVariableEvaluationException("Unable to find secret '" + key + "'. " +
-                "You should add it in your environment variables as 'SECRETS_" + key.toUpperCase()+"' with base64-encoded value."));
-        return new String(Base64.getDecoder().decode(environmentVariable));
+        if(decodedSecrets == null) {
+            decodedSecrets = new HashMap<>();
+        }
+
+        String decodedSecret = decodedSecrets.computeIfAbsent(
+            key,
+            (k) -> Optional.ofNullable(System.getenv("SECRETS_" + k.toUpperCase()))
+                .map(environmentVariable -> new String(Base64.getDecoder().decode(environmentVariable)))
+                .orElse(null)
+        );
+
+        if(decodedSecret == null){
+            throw new IllegalVariableEvaluationException("Unable to find secret '" + key + "'. " +
+                "You should add it in your environment variables as 'SECRETS_" + key.toUpperCase()+"' with base64-encoded value.");
+        }
+
+        return decodedSecret;
     }
 }