[#13] chain: Introduce ChainID type

Signed-off-by: aarifullin <aarifullin@yadro.com>

chain.go

@@ -13,7 +13,12 @@ type Engine interface {
 	IsAllowed(name Name, namespace string, r Request) (Status, bool)
 }
 
+// ChainID is the ID of rule chain.
+type ChainID string
+
 type Chain struct {
+	ID ChainID
+
 	Rules []Rule
 }
 

inmemory.go

@@ -1,6 +1,9 @@
 package policyengine
 
+import "sync/atomic"
+
 type inmemory struct {
+	chainCounter atomic.Uint32
 	namespace    map[Name][]chain
 	resource     map[Name][]chain
 	local        map[Name][]*Chain