Add config options to add authentication attributes as mdc.

docs/features/logback_mdc_level.md

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+# Set log level based on MDC values
+
+This can be used to change the log level based on MDC valus. E.g. change log levels for specific users/services etc.
+
+## Properties
+
+Property | Description | Default
+-------- | ----------- | -------
+`logger.mdc.enabled` | MDC enabled? | `true`
+`logger.mdc.<key>` | MDC key to use |
+`logger.mdc.<key>.key` | MDC key override, see complex example below for usage | `<key>`
+`logger.mdc.<key>.level` | log level to use | `TRACE`
+`logger.mdc.<key>.loggers` | passlist of logger names, matches all loggers if empty | `[]`
+`logger.mdc.<key>.values` | values for matching MDC key, matches all values if empty | `[]`
+
+## Examples
+
+Minimal configuration that logs everything with `TRACE` if MDC `principal` is present:
+
+```yaml
+logger:
+  levels:
+    io.kokuwa: INFO
+  mdc:
+    principal: {}
+```
+
+Configuration that logs everything with `TRACE` for logger `io.kokuwa` if MDC `gateway` matches one value:
+
+```yaml
+logger:
+  levels:
+    io.kokuwa: INFO
+  mdc:
+    gateway:
+      loggers:
+        - io.kokuwa
+      values:
+        - 257802b2-22fe-4dcc-bb99-c1db2a47861f
+        - 0a44738b-0c3a-4798-8210-2495485f10b2
+```
+
+Complex example with setting different values for different values/logger:
+
+```yaml
+logger:
+  levels:
+    io.kokuwa: INFO
+  mdc:
+    gateway-debug:
+      key: gateway
+      level: DEBUG
+      loggers:
+        - io.kokuwa
+      values:
+        - 6a1bae7f-eb6c-4c81-af9d-dc15396584e2
+        - fb3318f1-2c73-48e9-acd4-a2be3c9f9256
+    gateway-trace:
+      key: gateway
+      level: TRACE
+      loggers:
+        - io.kokuwa
+        - io.micronaut
+      values:
+        - 257802b2-22fe-4dcc-bb99-c1db2a47861f
+```