promtail: Move scrape_configs into prometheus_agent.agents.promtail.scrape_jobs dict

defaults/main.yml

@@ -51,15 +51,20 @@ prometheus_agent:
         positions:
           filename: /var/lib/promtail/positions.yaml
         # clients is generated based on prometheus_agent.scrapers
-        scrape_configs:
-        - job_name: system
+        # scrape_configs is generated based on prometheus_agent.agents.promtail.scrape_jobs
+      # "scrape_jobs" items have the same format as the "scrape_jobs" promtail
+      # config key. However, using a dictionary simplifies extending or changing
+      # the default scrape configs. Items with an empty value are ignored.
+      # The "job_name" field defaults to the item key.
+      scrape_jobs:
+        system:
           static_configs:
           - targets:
               - localhost
             labels:
               job: varlogs
               __path__: /var/log/*log
-        - job_name: journal
+        journal:
           journal:
             max_age: 12h
             labels:
@@ -72,14 +77,14 @@ prometheus_agent:
           pipeline_stages:
             - structured_metadata:
                 level:
-        - job_name: nginx
+        nginx:
           static_configs:
           - targets:
               - localhost
             labels:
               job: nginx
               __path__: /var/log/nginx/access-promtail.log
-        - job_name: postfix-bounces
+        postfix-bounces:
           static_configs:
           - targets:
               - localhost