refactor: move sentinel package to internal directory

Move the sentinel error definitions package from the root level to the
internal directory to indicate it's intended for internal use only.
This follows Go's internal package convention and prevents external
packages from depending on these error definitions directly.

Changes:
- Move sentinel/sentinel.go to internal/sentinel/sentinel.go
- Update all import statements across the codebase
- Maintain existing API and functionality unchanged

This change improves package organization by clearly marking the
sentinel package as internal implementation detail while preserving
all existing functionality and error handling behavior.

Author: hyp3rd

backend/inmemory.go

@@ -6,7 +6,7 @@ import (
 
 	cache "github.com/hyp3rd/hypercache/cache/v4"
 	"github.com/hyp3rd/hypercache/internal/constants"
-	"github.com/hyp3rd/hypercache/sentinel"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 	"github.com/hyp3rd/hypercache/types"
 )
 

backend/redis.go

@@ -10,8 +10,8 @@ import (
 	"github.com/hyp3rd/ewrap"
 
 	"github.com/hyp3rd/hypercache/internal/constants"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 	"github.com/hyp3rd/hypercache/libs/serializer"
-	"github.com/hyp3rd/hypercache/sentinel"
 	"github.com/hyp3rd/hypercache/types"
 )
 

eviction/arc.go

@@ -9,7 +9,7 @@ package eviction
 import (
 	"sync"
 
-	"github.com/hyp3rd/hypercache/sentinel"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 	"github.com/hyp3rd/hypercache/types"
 )
 

eviction/cawolfu.go

@@ -6,7 +6,7 @@ import (
 	"sync"
 
 	"github.com/hyp3rd/hypercache/cache"
-	"github.com/hyp3rd/hypercache/sentinel"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 )
 
 // CAWOLFU is an eviction algorithm that uses the Cache-Aware Write-Optimized LFU (CAWOLFU) policy to select items for eviction.

eviction/clock.go

@@ -9,7 +9,7 @@ package eviction
 import (
 	"sync"
 
-	"github.com/hyp3rd/hypercache/sentinel"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 	"github.com/hyp3rd/hypercache/types"
 )
 

eviction/eviction.go

@@ -5,7 +5,7 @@ import (
 
 	"github.com/hyp3rd/ewrap"
 
-	"github.com/hyp3rd/hypercache/sentinel"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 )
 
 // IAlgorithm is the interface that must be implemented by eviction algorithms.

eviction/lfu.go

@@ -6,7 +6,7 @@ import (
 	"container/heap"
 	"sync"
 
-	"github.com/hyp3rd/hypercache/sentinel"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 )
 
 // LFUAlgorithm is an eviction algorithm that uses the Least Frequently Used (LFU) policy to select items for eviction.

eviction/lru.go

@@ -13,7 +13,7 @@ package eviction
 import (
 	"sync"
 
-	"github.com/hyp3rd/hypercache/sentinel"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 )
 
 // lruCacheItem represents an item in the LRU cache.

factory.go

@@ -3,7 +3,7 @@ package hypercache
 import (
 	"github.com/hyp3rd/hypercache/backend"
 	"github.com/hyp3rd/hypercache/internal/constants"
-	"github.com/hyp3rd/hypercache/sentinel"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 )
 
 // IBackendConstructor is an interface for backend constructors.

hypercache.go

@@ -19,7 +19,7 @@ import (
 	"github.com/hyp3rd/hypercache/backend"
 	"github.com/hyp3rd/hypercache/eviction"
 	"github.com/hyp3rd/hypercache/internal/constants"
-	"github.com/hyp3rd/hypercache/sentinel"
+	"github.com/hyp3rd/hypercache/internal/sentinel"
 	"github.com/hyp3rd/hypercache/stats"
 	"github.com/hyp3rd/hypercache/types"
 	"github.com/hyp3rd/hypercache/utils"