platform and kots entitlement error msg (#69)

Author: smithers1221

client/entitlements.go

@@ -1,11 +1,26 @@
 package client
 
 import (
+	"errors"
+
 	"github.com/replicatedhq/replicated/pkg/types"
 )
 
 func (c *Client) CreateEntitlementSpec(name string, spec string, appID string) (*types.EntitlementSpec, error) {
-	return c.ShipClient.CreateEntitlementSpec(appID, name, spec)
+	appType, err := c.GetAppType(appID)
+	if err != nil {
+		return nil, err
+	}
+
+	if appType == "platform" {
+		return nil, errors.New("This feature is not supported for platform applications.")
+	} else if appType == "ship" {
+		c.ShipClient.CreateEntitlementSpec(appID, name, spec)
+	} else if appType == "kots" {
+		return nil, errors.New("This feature is not supported for kots applications.")
+	}
+
+	return nil, errors.New("unknown app type")
 }
 
 func (c *Client) SetDefaultEntitlementSpec(specID string) error {