added loki to our monitoring stack and updated the docs

docker-compose/monitoring-grafana-promethues-cadvisor-node-exporter/config.alloy

@@ -0,0 +1,40 @@
+// Discover all running Docker containers
+discovery.docker "containers" {
+  host = "unix:///var/run/docker.sock"
+}
+
+// Extract a clean "container" label from the container name
+discovery.relabel "containers" {
+  targets = discovery.docker.containers.targets
+
+  rule {
+    source_labels = ["__meta_docker_container_name"]
+    regex         = "/(.*)"
+    target_label  = "container"
+  }
+
+  rule {
+    source_labels = ["__meta_docker_container_name"]
+    regex         = "/(.*)"
+    target_label  = "container_name"
+  }
+
+  rule {
+    target_label = "instance"
+    replacement  = constants.hostname
+  }
+}
+
+// Tail logs from every discovered container
+loki.source.docker "containers" {
+  host       = "unix:///var/run/docker.sock"
+  targets    = discovery.relabel.containers.output
+  forward_to = [loki.write.default.receiver]
+}
+
+// Ship to the local Loki instance
+loki.write "default" {
+  endpoint {
+    url = "http://loki:3100/loki/api/v1/push"
+  }
+}