add promtail role

roles/promtail/templates/promtail.yml.j2

@@ -0,0 +1,28 @@
+{% if custom_server_config is defined %}
+{{ custom_server_config }}
+{% else %}
+server:
+  http_listen_port: {{ promtail_http_port }}
+  grpc_listen_port: 0
+{% endif %}
+positions:
+  filename: {{ promtail_positions_path }}
+
+clients:
+  - url: "http://{{  loki_server  }}:{{ loki_port }}/loki/api/v1/push"
+
+scrape_configs:
+{% if add_var_logs %}
+  - job_name: system
+    static_configs:
+      - targets:
+          - localhost
+        labels:
+          job: varlogs
+          __path__: /var/log/*log
+          host: {{ ansible_hostname }}
+{% endif %}
+
+{% if custom_scrape_configs is defined %}
+{{ custom_scrape_configs }}
+{% endif %}