Add test for custom settings in users.xml

tests/integration/helpers/0_common_instance_config.xml

 <yandex>
     <timezone>Europe/Moscow</timezone>
     <listen_host>0.0.0.0</listen_host>
+    <custom_settings_prefixes>custom_</custom_settings_prefixes>
     <path>/var/lib/clickhouse/</path>
     <tmp_path>/var/lib/clickhouse/tmp/</tmp_path>
 </yandex>

tests/integration/test_custom_settings/configs/config.d/text_log.xml

+<yandex>
+    <text_log/>
+</yandex>

tests/integration/test_custom_settings/configs/users.d/custom_settings.xml

+<yandex>
+    <profiles>
+        <default>
+            <custom_a>Int64_-5</custom_a>
+            <custom_b>UInt64_10000000000</custom_b>
+            <custom_c>Float64_-43.25e-1</custom_c>
+            <custom_d>'some text'</custom_d>
+        </default>
+
+        <profile_with_unknown_setting>
+            <x>1</x>
+        </profile_with_unknown_setting>
+
+        <profile_illformed_setting>
+            <custom_f>1</custom_f>
+        </profile_illformed_setting>
+    </profiles>
+</yandex>

tests/integration/test_custom_settings/test.py

+import pytest
+from helpers.cluster import ClickHouseCluster
+
+cluster = ClickHouseCluster(__file__)
+node = cluster.add_instance('node', config_dir='configs')
+
+
+@pytest.fixture(scope="module", autouse=True)
+def started_cluster():
+    try:
+        cluster.start()
+        yield cluster
+
+    finally:
+        cluster.shutdown()
+
+
+def test():
+    assert node.query("SELECT getSetting('custom_a')") == "-5\n"
+    assert node.query("SELECT getSetting('custom_b')") == "10000000000\n"
+    assert node.query("SELECT getSetting('custom_c')") == "-4.325\n"
+    assert node.query("SELECT getSetting('custom_d')") == "some text\n"
+
+    assert "custom_a = -5, custom_b = 10000000000, custom_c = -4.325, custom_d = \\'some text\\'" \
+        in node.query("SHOW CREATE SETTINGS PROFILE default")
+
+    assert "no settings profile" in node.query_and_get_error("SHOW CREATE SETTINGS PROFILE profile_with_unknown_setting")
+    assert "no settings profile" in node.query_and_get_error("SHOW CREATE SETTINGS PROFILE profile_illformed_setting")
+
+
+def test_invalid_settings():
+    node.query("SYSTEM RELOAD CONFIG")
+    node.query("SYSTEM FLUSH LOGS")
+
+    assert node.query("SELECT COUNT() FROM system.text_log WHERE"
+        " message LIKE '%Could not parse profile `profile_illformed_setting`%'"
+        " AND message LIKE '%Couldn\\'t restore Field from dump%'") == "1\n"
+
+    assert node.query("SELECT COUNT() FROM system.text_log WHERE"
+        " message LIKE '%Could not parse profile `profile_with_unknown_setting`%'"
+        " AND message LIKE '%Setting x is neither a builtin setting nor started with the prefix \\'custom_\\'%'") == "1\n"