Development: Use a more reasonable caching policy for plant uml renderings

Author: krusche

src/main/java/de/tum/cit/aet/artemis/programming/service/PlantUmlService.java

@@ -91,7 +91,7 @@ public byte[] generatePng(final String plantUml, final boolean useDarkTheme) thr
      * @return ResponseEntity PNG stream
      * @throws IOException if generateImage can't create the SVG
      */
-    @Cacheable(value = "plantUmlSvg", unless = "#result == null || #result.isEmpty()")
+    @Cacheable(value = "plantUmlSvg", unless = "#result == null || #result.isEmpty() || #result.contains('Syntax Error') || #result.contains('Cannot load')")
     public String generateSvg(final String plantUml, final boolean useDarkTheme) throws IOException {
         var input = validateInputAndApplyTheme(plantUml, useDarkTheme);
         try (final var bos = new ByteArrayOutputStream()) {

src/main/resources/config/application-prod.yml

@@ -89,7 +89,9 @@ server:
 jhipster:
     http:
         cache: # Used by the CachingHttpHeadersFilter
-            timeToLiveInDays: 1461
+            # 7 days balances caching benefits with allowing bug fixes to propagate within a reasonable timeframe.
+            # Longer durations (e.g., years) make it difficult to push fixes to users who have cached broken responses.
+            timeToLiveInDays: 7
     security:
         authentication:
             jwt:

src/main/resources/config/application.yml

@@ -382,7 +382,9 @@ jhipster:
         password: AN-ADMIN-PASSWORD-THAT-MUST-BE-CHANGED (FROM REGISTRY CONFIG)
     http:
         cache: # Used by the CachingHttpHeadersFilter
-            timeToLiveInDays: 1461
+            # 7 days balances caching benefits with allowing bug fixes to propagate within a reasonable timeframe.
+            # Longer durations (e.g., years) make it difficult to push fixes to users who have cached broken responses.
+            timeToLiveInDays: 7
     cache: # Cache configuration
         hazelcast: # Hazelcast distributed cache
             time-to-live-seconds: 3600