feat: comprehensive audit log

config/packages/monolog.yaml

@@ -1,6 +1,21 @@
 monolog:
     channels: # To see all channels, run bin/console debug:autowiring logger
         - deprecation # Deprecations are logged in the dedicated "deprecation" channel when it exists
+        - audit # Who did what to a booking or a resource -- see App\Service\AuditLogger
+
+    handlers:
+        # The audit trail is kept in every environment, on its own file and for 30 days. It is
+        # deliberately not routed through the handlers below: those are fingers_crossed in prod,
+        # which means records are dropped unless an error happens to flush the buffer -- fine for
+        # debug noise, useless for a trail that has to be complete. Hence the plain handler, and
+        # hence "!audit" on the others so the same record is not duplicated into them.
+        audit:
+            type: rotating_file
+            path: "%kernel.logs_dir%/audit.%kernel.environment%.log"
+            max_files: 30
+            level: info
+            channels: [audit]
+            formatter: monolog.formatter.json
 
 when@dev:
     monolog:
@@ -9,11 +24,11 @@ when@dev:
                 type: stream
                 path: "%kernel.logs_dir%/%kernel.environment%.log"
                 level: debug
-                channels: ["!event"]
+                channels: ["!event", "!audit"]
             console:
                 type: console
                 process_psr_3_messages: false
-                channels: ["!event", "!doctrine", "!console"]
+                channels: ["!event", "!doctrine", "!console", "!audit"]
 
 when@test:
     monolog:
@@ -23,7 +38,7 @@ when@test:
                 action_level: error
                 handler: nested
                 excluded_http_codes: [404, 405]
-                channels: ["!event"]
+                channels: ["!event", "!audit"]
             nested:
                 type: stream
                 path: "%kernel.logs_dir%/%kernel.environment%.log"
@@ -37,7 +52,7 @@ when@prod:
                 action_level: error
                 handler: nested
                 excluded_http_codes: [404, 405]
-                channels: ["!deprecation"]
+                channels: ["!deprecation", "!audit"]
                 buffer_size: 50 # How many messages should be saved? Prevent memory leaks
             nested:
                 type: stream
@@ -47,7 +62,7 @@ when@prod:
             console:
                 type: console
                 process_psr_3_messages: false
-                channels: ["!event", "!doctrine"]
+                channels: ["!event", "!doctrine", "!audit"]
             deprecation:
                 type: stream
                 channels: [deprecation]

config/services.yaml

@@ -19,6 +19,13 @@ services:
     App\:
         resource: '../src/'
 
+    # The audit trail writes to its own channel, never to the default one: the rotating
+    # audit.*.log is the record of who moved what, and mixing framework noise into it (or the
+    # trail into the framework log) would defeat both.
+    App\Service\AuditLogger:
+        arguments:
+            $logger: '@monolog.logger.audit'
+
     # The myep OAuth2 client. Endpoint URLs are configuration rather than constants (same as
     # myep-team), so dev, staging and production differ by .env alone. Empty credentials are a
     # valid state: the login page then says the client is not registered yet instead of bouncing