Final changes to config sub-system (#8600)

- Introduces changes such as certain types of
  errors that can be ignored or which need to 
  go into safe mode.
- Update help text as per the review

cmd/config/policy/opa/config.go

@@ -41,10 +41,6 @@ const (
 // DefaultKVS - default config for OPA config
 var (
 	DefaultKVS = config.KVS{
-		config.KV{
-			Key:   config.State,
-			Value: config.StateOff,
-		},
 		config.KV{
 			Key:   URL,
 			Value: "",
@@ -112,6 +108,11 @@ type Opa struct {
 	client *http.Client
 }
 
+// Enabled returns if opa is enabled.
+func Enabled(kvs config.KVS) bool {
+	return kvs.Get(URL) != ""
+}
+
 // LookupConfig lookup Opa from config, override with any ENVs.
 func LookupConfig(kv config.KVS, transport *http.Transport, closeRespFn func(io.ReadCloser)) (Args, error) {
 	args := Args{}

cmd/config/policy/opa/help.go

@@ -23,18 +23,18 @@ var (
 	Help = config.HelpKVS{
 		config.HelpKV{
 			Key:         URL,
-			Description: `Points to URL for OPA HTTP API endpoint. eg: "http://localhost:8181/v1/data/httpapi/authz/allow"`,
+			Description: `OPA HTTP API endpoint e.g. "http://localhost:8181/v1/data/httpapi/authz/allow"`,
 			Type:        "url",
 		},
 		config.HelpKV{
 			Key:         AuthToken,
-			Description: "Authorization token for the OPA HTTP API endpoint",
+			Description: "authorization token for OPA HTTP API endpoint",
 			Optional:    true,
 			Type:        "string",
 		},
 		config.HelpKV{
 			Key:         config.Comment,
-			Description: "A comment to describe the OPA policy setting",
+			Description: config.DefaultComment,
 			Optional:    true,
 			Type:        "sentence",
 		},

cmd/config/policy/opa/legacy.go

@@ -33,10 +33,6 @@ func SetPolicyOPAConfig(s config.Config, opaArgs Args) {
 		return
 	}
 	s[config.PolicyOPASubSys][config.Default] = config.KVS{
-		config.KV{
-			Key:   config.State,
-			Value: config.StateOn,
-		},
 		config.KV{
 			Key:   URL,
 			Value: opaArgs.URL.String(),