feat: add file logging (#2023)

logs into `lnbits.log` with info loglevel and `debug.log` with DEBUG loglevel
files will be saved into `LNBITS_DATA_DIR`.
retentions is configurable but defaults to `90 days`
* added log rotation aswell

---------

Co-authored-by: Vlad Stan <stan.v.vlad@gmail.com>

lnbits/app.py

@@ -526,6 +526,23 @@ def configure_logger() -> None:
     log_level: str = "DEBUG" if settings.debug else "INFO"
     formatter = Formatter()
     logger.add(sys.stdout, level=log_level, format=formatter.format)
+
+    if settings.enable_log_to_file:
+        logger.add(
+            Path(settings.lnbits_data_folder, "logs", "lnbits.log"),
+            rotation=settings.log_rotation,
+            retention=settings.log_retention,
+            level="INFO",
+            format=formatter.format,
+        )
+        logger.add(
+            Path(settings.lnbits_data_folder, "logs", "debug.log"),
+            rotation=settings.log_rotation,
+            retention=settings.log_retention,
+            level="DEBUG",
+            format=formatter.format,
+        )
+
     logging.getLogger("uvicorn").handlers = [InterceptHandler()]
     logging.getLogger("uvicorn.access").handlers = [InterceptHandler()]
     logging.getLogger("uvicorn.error").handlers = [InterceptHandler()]