Added initial infrastructure for declarative prometheus configs and established alloy integration for Traefik

nix-system-configs/modules/system/traefik.nix

@@ -93,10 +93,47 @@ in {
       };
     };
 
+    services.alloy = {
+      enable = true;
+    };
+
+    # See: https://github.com/grafana/alloy/blob/bbe11b0f6a3bd3391108b2d27122c654c535dd8d/docs/sources/set-up/migrate/from-promtail.md
+    environment.etc."alloy/config.alloy" = {
+      text = ''
+        discovery.relabel "metrics_integrations_integrations_traefik" {
+        	targets = [{
+        		__address__ = "localhost:8080",
+        	}]
+
+        	rule {
+        		target_label = "instance"
+        		replacement  = constants.hostname
+        	}
+        }
+
+        prometheus.scrape "metrics_integrations_integrations_traefik" {
+        	targets    = discovery.relabel.metrics_integrations_integrations_traefik.output
+        	forward_to = [prometheus.remote_write.metrics_service.receiver]
+        	job_name   = "integrations/traefik"
+        }
+      '';
+      group = "root";
+      mode = "0644";
+    };
+
     services.traefik = {
       enable = true;
       group = "acme";
       staticConfigOptions = {
+        metrics = {
+          prometheus = {
+            addEntryPointsLabels = true;
+            addRoutersLabels = true;
+            addServicesLabels = true;
+            entryPoint = "metrics";
+          };
+        };
+
         entryPoints = {
           web = {
             # Bind on IPv6 as well as IPv4 by using [::]:80