Docs: TLS Negotiated Group Metrics (#12415)

Author: masaori335

doc/admin-guide/monitoring/statistics/core-statistics.en.rst

@@ -40,6 +40,7 @@ component to which they're related.
    core/network-io.en
    core/ssl.en
    core/ssl-cipher.en
+   core/ssl-group.en
    core/http-transaction.en
    core/http-response-code.en
    core/http-request-method.en

doc/admin-guide/monitoring/statistics/core/ssl-group.en.rst

@@ -0,0 +1,65 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+   or more contributor license agreements.  See the NOTICE file
+   distributed with this work for additional information
+   regarding copyright ownership.  The ASF licenses this file
+   to you under the Apache License, Version 2.0 (the
+   "License"); you may not use this file except in compliance
+   with the License.  You may obtain a copy of the License at
+
+   http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing,
+   software distributed under the License is distributed on an
+   "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+   KIND, either express or implied.  See the License for the
+   specific language governing permissions and limitations
+   under the License.
+
+.. include:: ../../../../common.defs
+
+.. _admin-stats-core-ssl-group:
+
+TLS Negotiated Group
+********************
+
+The following statistics provide individual counters for the number of TLS negotiated group with client.
+Some groups do not appear if linked TLS library doesn't support them.
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.ffdhe2048 integer integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.ffdhe3072 integer integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.ffdhe4096 integer integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.ffdhe6144 integer integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.ffdhe8192 integer integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.P-224 integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.P-256 integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.P-384 integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.P-521 integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.X448 integer integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.X25519 integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.X25519MLKEM768 integer
+   :type: counter
+
+.. ts:stat:: global proxy.process.ssl.group.user_agent.OTHER integer
+   :type: counter