[core] Adding toggle for CORS, GZIP in admin/cms configuration (#30)

This PR enables admins to disable/enable CORS and GZIP from within the admin CMS configuration page. Both are enabled by default.

Note: currently, the GZIP implementation is 100% on the fly, for every qualifying API endpoint request. This could add significant CPU usage, but dramatically decreases bandwidth. Will be considering other better implementations, but for now YMMV.

Possible optimizations:
- pooling gzip Writers vs. creating a new one for each response
- caching gzipped responses (in memory? on disk?) 
- enforcing size threshold (only gzip content larger than N bytes) 

1 files changed, 18 insertions, 4 deletions

diff --git a/system/db/addon.go b/system/db/addon.go
index f4621fa..0f63405 100644
--- a/system/db/addon.go
+++ b/system/db/addon.go
@@ -24,6 +24,9 @@ func Addon(key string) ([]byte, error) {
 
 	err := store.View(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte("__addons"))
+		if b == nil {
+			return bolt.ErrBucketNotFound
+		}
 
 		val := b.Get([]byte(key))
 
@@ -56,12 +59,16 @@ func SetAddon(data url.Values, kind interface{}) error {
 
 	v, err := json.Marshal(kind)
 
+	k := data.Get("addon_reverse_dns")
+	if k == "" {
+		name := data.Get("addon_name")
+		return fmt.Errorf(`Addon "%s" has no identifier to use as key.`, name)
+	}
+
 	err = store.Update(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte("__addons"))
-		k := data.Get("addon_reverse_dns")
-		if k == "" {
-			name := data.Get("addon_name")
-			return fmt.Errorf(`Addon "%s" has no identifier to use as key.`, name)
+		if b == nil {
+			return bolt.ErrBucketNotFound
 		}
 
 		err := b.Put([]byte(k), v)
@@ -84,6 +91,10 @@ func AddonAll() [][]byte {
 
 	err := store.View(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte("__addons"))
+		if b == nil {
+			return bolt.ErrBucketNotFound
+		}
+
 		err := b.ForEach(func(k, v []byte) error {
 			all = append(all, v)
 
@@ -107,6 +118,9 @@ func AddonAll() [][]byte {
 func DeleteAddon(key string) error {
 	err := store.Update(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte("__addons"))
+		if b == nil {
+			return bolt.ErrBucketNotFound
+		}
 
 		if err := b.Delete([]byte(key)); err != nil {
 			return err