Align S3 backend with metrics framework

- Add metrics parameter to _S3Core.__init__()
- Pass metrics to S3 core in cachier decorator
- Add metrics import to s3.py
- Update S3 core docstring to document metrics parameter
- Ensures S3 backend supports metrics like all other backends

Addresses comment 4010458432: aligns with latest codebase

Co-authored-by: Borda <6035284+Borda@users.noreply.github.com>

Author: Copilot

src/cachier/core.py

@@ -373,6 +373,7 @@ def cachier(
             s3_endpoint_url=s3_endpoint_url,
             s3_config=s3_config,
             entry_size_limit=size_limit_bytes,
+            metrics=cache_metrics,
         )
     else:
         raise ValueError("specified an invalid core: %s" % backend)

src/cachier/cores/s3.py

@@ -20,6 +20,11 @@
 from ..config import CacheEntry
 from .base import RecalculationNeeded, _BaseCore, _get_func_str
 
+try:
+    from ..metrics import CacheMetrics
+except ImportError:
+    CacheMetrics = None  # type: ignore[assignment,misc]
+
 S3_SLEEP_DURATION_IN_SEC = 1
 
 
@@ -62,6 +67,8 @@ class _S3Core(_BaseCore):
         Optional ``botocore.config.Config`` object passed when creating the client.
     entry_size_limit : int, optional
         Maximum allowed size in bytes of a cached value.
+    metrics : CacheMetrics, optional
+        Metrics collector for tracking cache performance.
 
     """
 
@@ -77,6 +84,7 @@ def __init__(
         s3_endpoint_url: Optional[str] = None,
         s3_config: Optional[Any] = None,
         entry_size_limit: Optional[int] = None,
+        metrics: Optional["CacheMetrics"] = None,
     ):
         if not BOTO3_AVAILABLE:
             _safe_warn(
@@ -88,6 +96,7 @@ def __init__(
             hash_func=hash_func,
             wait_for_calc_timeout=wait_for_calc_timeout,
             entry_size_limit=entry_size_limit,
+            metrics=metrics,
         )
 
         if not s3_bucket: