allow configuration of secrets for alertmanager (#2206)

jsonnet/kube-prometheus/components/alertmanager.libsonnet

@@ -60,6 +60,7 @@ local defaults = {
     ],
   },
   replicas: 3,
+  secrets: [],
   mixin:: {
     ruleLabels: {},
     _config: {
@@ -225,6 +226,7 @@ function(params) {
       },
       resources: am._config.resources,
       nodeSelector: { 'kubernetes.io/os': 'linux' },
+      secrets: am._config.secrets,
       serviceAccountName: am.serviceAccount.metadata.name,
       securityContext: {
         runAsUser: 1000,

manifests/alertmanager-alertmanager.yaml

@@ -28,6 +28,7 @@ spec:
     requests:
       cpu: 4m
       memory: 100Mi
+  secrets: []
   securityContext:
     fsGroup: 2000
     runAsNonRoot: true