Extract metric name normalization into rabbit_prometheus_util

Move `normalize_disabled_metrics/1` and `normalize_metric_name/1` from
`prometheus_rabbitmq_core_metrics_collector` into a new
`rabbit_prometheus_util` module so that the functions are properly
exported and testable.

Update `rabbit_prometheus_disabled_metrics_SUITE` to call
`rabbit_prometheus_util:normalize_metric_name/1` directly instead of
duplicating the implementation locally.

Author: lukebakken

deps/rabbitmq_prometheus/src/collectors/prometheus_rabbitmq_core_metrics_collector.erl

@@ -477,7 +477,7 @@ add_metric_family({Name, Type, Help, Metrics}, Callback) ->
     Callback(create_mf(MN, Help, Type, Metrics)).
 
 mf(Callback, Prefix, Contents, Data) ->
-    DisabledMetrics = normalize_disabled_metrics(application:get_env(rabbitmq_prometheus, disabled_metrics, [])),
+    DisabledMetrics = rabbit_prometheus_util:normalize_disabled_metrics(application:get_env(rabbitmq_prometheus, disabled_metrics, [])),
     _ = [begin
          Fun = case Conversion of
                    undefined ->
@@ -513,17 +513,6 @@ mf(Callback, Prefix, Contents, Data) ->
         )
     end || {Index, Conversion, Name, Type, Help, Key} <- Contents, not lists:member(Name, DisabledMetrics)].
 
-normalize_disabled_metrics(Metrics) ->
-    [normalize_metric_name(M) || M <- Metrics].
-
-normalize_metric_name(Metric) when is_atom(Metric) ->
-    case atom_to_list(Metric) of
-        "rabbitmq_detailed_" ++ Rest -> list_to_atom(Rest);
-        "rabbitmq_cluster_" ++ Rest -> list_to_atom(Rest);
-        "rabbitmq_" ++ Rest -> list_to_atom(Rest);
-        _ -> Metric
-    end.
-
 mf_totals(Callback, Name, Type, Help, Size) ->
     Callback(
         create_mf(

deps/rabbitmq_prometheus/src/rabbit_prometheus_util.erl

@@ -0,0 +1,24 @@
+%% This Source Code Form is subject to the terms of the Mozilla Public
+%% License, v. 2.0. If a copy of the MPL was not distributed with this
+%% file, You can obtain one at https://mozilla.org/MPL/2.0/.
+%%
+%% Copyright (c) 2007-2026 Broadcom. All Rights Reserved. The term "Broadcom" refers to Broadcom Inc. and/or its subsidiaries. All rights reserved.
+%%
+
+-module(rabbit_prometheus_util).
+
+-export([normalize_disabled_metrics/1,
+         normalize_metric_name/1]).
+
+-spec normalize_disabled_metrics([atom()]) -> [atom()].
+normalize_disabled_metrics(Metrics) ->
+    [normalize_metric_name(M) || M <- Metrics].
+
+-spec normalize_metric_name(atom()) -> atom().
+normalize_metric_name(Metric) when is_atom(Metric) ->
+    case atom_to_list(Metric) of
+        "rabbitmq_detailed_" ++ Rest -> list_to_atom(Rest);
+        "rabbitmq_cluster_" ++ Rest  -> list_to_atom(Rest);
+        "rabbitmq_" ++ Rest          -> list_to_atom(Rest);
+        _                            -> Metric
+    end.

deps/rabbitmq_prometheus/test/rabbit_prometheus_disabled_metrics_SUITE.erl

@@ -110,18 +110,10 @@ disable_multiple_metrics_test(Config) ->
     ?assertEqual(nomatch, re:run(Body, "^rabbitmq_connection_incoming_bytes_total ", [{capture, none}, multiline])).
 
 normalize_metric_name_test(_Config) ->
-    ?assertEqual(queue_messages, normalize_metric_name(rabbitmq_queue_messages)),
-    ?assertEqual(queue_messages, normalize_metric_name(rabbitmq_detailed_queue_messages)),
-    ?assertEqual(vhost_status, normalize_metric_name(rabbitmq_cluster_vhost_status)),
-    ?assertEqual(other_metric, normalize_metric_name(other_metric)).
-
-normalize_metric_name(Metric) when is_atom(Metric) ->
-    case atom_to_list(Metric) of
-        "rabbitmq_detailed_" ++ Rest -> list_to_atom(Rest);
-        "rabbitmq_cluster_" ++ Rest -> list_to_atom(Rest);
-        "rabbitmq_" ++ Rest -> list_to_atom(Rest);
-        _ -> Metric
-    end.
+    ?assertEqual(queue_messages, rabbit_prometheus_util:normalize_metric_name(rabbitmq_queue_messages)),
+    ?assertEqual(queue_messages, rabbit_prometheus_util:normalize_metric_name(rabbitmq_detailed_queue_messages)),
+    ?assertEqual(vhost_status, rabbit_prometheus_util:normalize_metric_name(rabbitmq_cluster_vhost_status)),
+    ?assertEqual(other_metric, rabbit_prometheus_util:normalize_metric_name(other_metric)).
 
 %% Helpers