Viraj/metrics lambda (#348)

* OB-36691 feat: add lambda and s3 bucket to record push metrics config

apps/stack/template.yaml

@@ -37,6 +37,11 @@ Metadata:
           default: CloudWatch Metrics
         Parameters:
           - MetricStreamFilterUri
+          - ObserveAccountID
+          - ObserveDomainName
+          - DatasourceID
+          - GQLToken
+          - UpdateTimestamp
       - Label:
           default: Forwarder Options
         Parameters:
@@ -109,9 +114,10 @@ Parameters:
       S3 URI containing filters for metrics to be collected by CloudWatch
       Metrics Stream. If neither this nor DatasourceID is provided, no metrics
       will be collected.
-    Default: 's3://observeinc/cloudwatchmetrics/filters/empty.yaml'
-    # the empty.yaml file functions as a sentinel value: it lists a namespace
-    # that does not exist, and this causes no metrics to be collected.
+    Default: 's3://observeinc/cloudwatchmetrics/filters/recommended.yaml'
+    # Not used: if no MetricStreamFilterUri is provided, the Metric Stream
+    # nested stack will not be deployed. This value is used as a sensible
+    # default in case the above changes.
     AllowedPattern: "^(s3:\/\/.*)?$"
   ObserveAccountID:
     # this and the field below are necessary for us to be able to make a