grafana: Enable Unified Alerting and wire up with alertmanager

Grafana v8.2.0 added support for Prometheus's Alertmanager[1] which can
be used with the Unified Alerting added in v8.0.0[2].

[1] https://github.com/grafana/grafana/releases/tag/v8.2.0
[2] https://grafana.com/blog/2021/06/08/grafana-8.0-unified-grafana-and-prometheus-alerts-live-streaming-new-visualizations-and-more/

roles/grafana/templates/datasources.yaml.j2

@@ -19,4 +19,12 @@ datasources:
   type: loki
   access: proxy
   url: http://localhost:3100
+  jsonData:
+    manageAlerts: false
+- name: Alertmanager
+  type: alertmanager
+  access: proxy
+  url: http://localhost:9093
+  jsonData:
+    implementation: prometheus
 {% endif %}

roles/grafana/templates/grafana.ini.j2

@@ -716,7 +716,7 @@ mode = syslog
 #################################### Unified Alerting ####################
 [unified_alerting]
 #Enable the Unified Alerting sub-system and interface. When enabled we'll migrate all of your alert rules and notification channels to the new system. New alert rules will be created and your notification channels will be converted into an Alertmanager configuration. Previous data is preserved to enable backwards compatibility but new data is removed.```
-;enabled = false
+enabled = true
 
 # Comma-separated list of organization IDs for which to disable unified alerting. Only supported if unified alerting is enabled.
 ;disabled_orgs = 
@@ -940,7 +940,7 @@ enabled = false
 ;disable_sanitize_html = false
 
 [plugins]
-;enable_alpha = false
+enable_alpha = true
 ;app_tls_skip_verify_insecure = false
 # Enter a comma-separated list of plugin identifiers to identify plugins to load even if they are unsigned. Plugins with modified signatures are never loaded.
 ;allow_loading_unsigned_plugins =