Add gocritic linter (#1324)

* Add gocritic linter

`gocritic` provides diagnostics that check for bugs, performance, and style issues

We disable the following checks:

- commentFormatting
- captLocal
- deprecatedComment

This PR contains many `//nolint:gocritic` to disable `appendAssign`.

management/server/http/policies_handler.go

@@ -300,7 +300,7 @@ func toPolicyResponse(account *server.Account, policy *server.Policy) *api.Polic
 			Action:        api.PolicyRuleAction(r.Action),
 		}
 		if len(r.Ports) != 0 {
-			portsCopy := r.Ports[:]
+			portsCopy := r.Ports
 			rule.Ports = &portsCopy
 		}
 		for _, gid := range r.Sources {

management/server/http/setupkeys_handler.go

@@ -192,13 +192,14 @@ func writeSuccess(w http.ResponseWriter, key *server.SetupKey) {
 
 func toResponseBody(key *server.SetupKey) *api.SetupKey {
 	var state string
-	if key.IsExpired() {
+	switch {
+	case key.IsExpired():
 		state = "expired"
-	} else if key.IsRevoked() {
+	case key.IsRevoked():
 		state = "revoked"
-	} else if key.IsOverUsed() {
+	case key.IsOverUsed():
 		state = "overused"
-	} else {
+	default:
 		state = "valid"
 	}