feat(common): add errors to be used in validation throughout

common/error.go

@@ -0,0 +1,15 @@
+package common
+
+import "errors"
+
+// Common errors
+var (
+    ErrInvalidUrl      = errors.New("url is invalid")
+    ErrInvalidUrlLen   = errors.New("url is too short or too long, should be 7-2048 chars")
+    ErrBlacklistedUrl  = errors.New("url matches blacklist pattern")
+    ErrKeywordsCount   = errors.New("url must not have more than 10 keywords")
+    ErrKeywordLength   = errors.New("keyword must contain 2-25 characters")
+    ErrInvalidDate     = errors.New("expires_on should be in 'yyyy-mm-dd hh:mm:ss' format")
+    ErrPastExpiration  = errors.New("expires_on can not be date in past")
+    ErrUrlAlreadyShort = errors.New("the url is already shortened")
+)