Issue 6227 - dsconf schema does not show inChain matching rule

Bug description:
	The registered inChain MR does defined any matching rule
	syntax (mr_syntax).
	When dsconf reads the matching rules (read_schema_dse)
	it only reports those which have OID and SYNTAX.
	As a consequence InChain was not reported.

Fix description:
	The syntax defines that assersion syntax that is
	distinguished name. Add this syntax to the register
	struct

relates: 389ds#6227

Reviewed by:

dirsrvtests/tests/suites/filter/inchain_test.py

@@ -812,6 +812,27 @@ def test_invalid_assertion(topo):
     memberof = topo.standalone.search_s(DEFAULT_SUFFIX, SCOPE_SUBTREE, "(member:%s:=%s)" % (INCHAIN_OID, user))
     assert len(memberof) == 0
 
+def test_check_dsconf_matchingrule(topo):
+    """Test that the matching rule 'inchain' is listed by dsconf
+
+    :id: b8dd4049-ccec-4316-bc9c-5aa5c5afcfbd
+    :setup: Standalone Instance
+    :steps:
+        1. run 'dsconf instance schema matchingrules list'
+        2. Checks that the output contains inchaineMatch matching rule
+    :expectedresults:
+        1. Success
+        2. Success
+    """
+    dsconf_cmd= ['/usr/sbin/dsconf', topo.standalone.serverid, 'schema', 'matchingrules', 'list']
+    # Set referral
+    log.info("Use dsconf to check defined matching rules")
+    log.info(f'Command used: %{dsconf_cmd}')
+    proc = subprocess.Popen(dsconf_cmd, stdout=subprocess.PIPE)
+    out, _ = proc.communicate()
+    log.info('output message : %s' % out[0])
+    assert '1.2.840.113556.1.4.1941 NAME \'inchainMatch\'' in out.decode('utf-8')
+
 if __name__ == "__main__":
     CURRENT_FILE = os.path.realpath(__file__)
     pytest.main("-s -v %s" % CURRENT_FILE)

ldap/servers/plugins/syntaxes/inchain.c

@@ -38,7 +38,7 @@ static char *names[] = {"inchain", "inchain", LDAP_MATCHING_RULE_IN_CHAIN_OID, 0
 static Slapi_PluginDesc pdesc = {"inchain-matching-rule", VENDOR, DS_PACKAGE_VERSION,
                                  "inchain matching rule plugin"};
 
-static const char *inchainMatch_names[] = {"inchainMatch", "1.2.840.113556.1.4.1941", NULL};
+static const char *inchainMatch_names[] = {"inchainMatch", LDAP_MATCHING_RULE_IN_CHAIN_OID, NULL};
 
 static struct mr_plugin_def mr_plugin_table[] = {
     {
@@ -64,7 +64,7 @@ static struct mr_plugin_def mr_plugin_table[] = {
             "the AVA comparisons evaluate to Undefined and the remaining AVA "
             "comparisons return TRUE then the distinguishedNameMatch rule "
             "evaluates to Undefined.",
-            NULL,
+            DN_SYNTAX_OID,
             0,
             NULL /* dn only for now */
         },       /* matching rule desc */