feat(logs): provide an option to keep all logs (#6644)

Author: eliandoran

apps/server/src/services/log.ts

@@ -38,6 +38,9 @@ async function cleanupOldLogFiles() {
         const customRetentionDays = config.Logging.retentionDays;
         if (customRetentionDays > 0) {
             retentionDays = customRetentionDays;
+        } else if (customRetentionDays <= -1){
+            info(`Log cleanup: keeping all log files, as specified by configuration.`);
+            return
         }
 
         const cutoffDate = new Date();

docs/User Guide/User Guide/Troubleshooting/Error logs/Backend (server) logs.md

@@ -1,4 +1,4 @@
-# Backend (server) logs
+# Backend (server) logs
 ## Accessing via the backend log
 
 In the <a class="reference-link" href="../../Basic%20Concepts%20and%20Features/UI%20Elements/Global%20menu.md">Global menu</a>, go to Advanced → Show backend log
@@ -24,5 +24,11 @@ retentionDays=7
 
 Or via the environment variable `TRILIUM_LOGGING_RETENTION_DAYS`.
 
+Special cases:
+
+*   Positive values indicate the number of days worth of logs to keep
+*   A value of 0 results with the default value (90 days) to be used
+*   Negative values (e.g. `-1`) result with all logs to be kept, irrespective how ancient and numerous (and
+
 > [!NOTE]
 > If you set the retention days to a low number, you might notice that not all the log files are being deleted. This is because a minimum number of logs (7 at the time of writing) is maintained at all times.