feat(backend-common): support custom logger options

.changeset/fluffy-nails-sort.md

@@ -0,0 +1,25 @@
+---
+'@backstage/backend-common': patch
+---
+
+Updated the `rootLogger` in `@backstage/backend-common` to support custom logging options. This is useful when you want to make some changes without re-implementing the entire logger and calling `setRootLogger` or `logger.configure`. For example you can add additional `defaultMeta` tags to each log entry. The following changes are included:
+
+- Added `createRootLogger` which accepts winston `LoggerOptions`. These options allow overriding the default keys.
+- Added an additional error format that can include stack traces. This can be enabled by setting a `LOG_STACKTRACE=true` environment variable. Any `Error` objects passed to `logger.error('message', err)` will include the full stack trace in a `stack` log entry key.
+
+Example Usage:
+
+```ts
+// Create the logger
+const logger = createRootLogger({
+  defaultMeta: { appName: 'backstage', appEnv: 'prod' },
+});
+
+// Add a custom logger transport
+logger.add(new MyCustomTransport());
+
+const config = await loadBackendConfig({
+  argv: process.argv,
+  logger: getRootLogger(), // already set to new logger instance
+});
+```