feat: cache + paths (#1)

- Added helper function `ExpandUser`
- Added basic cache impmentations for in-memory and file based caches.

Reviewed-on: #1
Co-authored-by: Felipe M. <me@fmartingr.com>
Co-committed-by: Felipe M. <me@fmartingr.com>

cache/options.go

@@ -0,0 +1,14 @@
+package cache
+
+import (
+	"time"
+
+	"git.nakama.town/fmartingr/gotoolkit/model"
+)
+
+func WithTTL(ttl time.Duration) model.CacheOption {
+	return func(item *model.CacheItem) {
+		exp := time.Now().Add(ttl)
+		item.TTL = &exp
+	}
+}