add utility function for getting from cache with metrics

Author: FormJani

django_prometheus/cache/backends/utils.py

@@ -0,0 +1,16 @@
+from django_prometheus.cache.metrics import (
+    django_cache_get_total,
+    django_cache_hits_total,
+    django_cache_misses_total,
+)
+
+
+def cache_get_with_metrics(*, key, backend_name, default=None, version=None):
+        django_cache_get_total.labels(backend=backend_name).inc()
+        cached = super().get(key, default=None, version=version)
+        if cached is not None:
+            django_cache_hits_total.labels(backend=backend_name).inc()
+            return cached
+
+        django_cache_misses_total.labels(backend=backend_name).inc()
+        return default