Add metric audit log configuration to readme

Author: mirskifa

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Updated to MQ version 9.4.3.0
 * Refactored the file permission logs to match the container logging format
+* Allow enabling audit logging of access to Prometheus metrics endpoint (enable audit logging by setting `MQ_LOGGING_METRICS_AUDIT_ENABLED=true`)
 
 ## 9.4.2.0 (2025-02)
 

README.md

@@ -31,6 +31,7 @@ Note that in order to use the image, it is necessary to accept the terms of the
 - **MQ_LOGGING_CONSOLE_SOURCE** - Specifies a comma-separated list of sources for logs which are mirrored to the container's stdout. The valid values are "qmgr", "web" and "mqsc". Defaults to "qmgr,web". 
 - **MQ_LOGGING_CONSOLE_FORMAT** - Changes the format of the logs which are printed on the container's stdout.  Set to "json" to use JSON format (JSON object per line); set to "basic" to use a simple human-readable format.  Defaults to "basic".
 - **MQ_LOGGING_CONSOLE_EXCLUDE_ID** - Excludes log messages with the specified ID.  The log messages still appear in the log file on disk, but are excluded from the container's stdout.  Defaults to "AMQ5041I,AMQ5052I,AMQ5051I,AMQ5037I,AMQ5975I".
+- **MQ_LOGGING_METRICS_AUDIT_ENABLED** - Set this to `true` to enable audit logging of access to the Prometheus metrics endpoint. Log output is to a JSON file in `/var/mqm/errors/`. Requires that `MQ_ENABLE_METRICS=true` is also set.
 - **MQ_ENABLE_METRICS** - Set this to `true` to generate Prometheus metrics for your Queue Manager.
 
 See the [default developer configuration docs](docs/developer-config.md) for the extra environment variables supported by the MQ Advanced for Developers image.