MT#63027 repoapi: use LDAP search with recursion for user retrieval

Switch from AUTH_LDAP_USER_DN_TEMPLATE to AUTH_LDAP_USER_SEARCH,
so we're more flexible:

AUTH_LDAP_USER_DN_TEMPLATE builds the user's DN (Distinguished Name)
directly from a template, without searching though (it assumes you know
the exact DN structure). While being faster, it's also less flexible.

AUTH_LDAP_USER_SEARCH on the other hand performs an LDAP search to find
the user, and by enabling SCOPE_SUBTREE we can also enable recursion.

This change is required to provide e.g. Jose from operations access
to our repoapi.

Also see MT#54080 for some historic information about those changes.

Change-Id: I30b3a3a5801ec3321ac67e533c32e5d4682c1ce3

repoapi/settings/prod.py

@@ -85,7 +85,11 @@ AUTH_LDAP_REQUIRE_GROUP_LIST = server_config.get(
     "server", "AUTH_LDAP_REQUIRE_GROUP_LIST"
 ).split(",")
 require_grp_list_size = len(AUTH_LDAP_REQUIRE_GROUP_LIST)
-AUTH_LDAP_USER_DN_TEMPLATE = "uid=%(user)s," + AUTH_LDAP_USER_BASE
+AUTH_LDAP_USER_SEARCH = LDAPSearch(
+    AUTH_LDAP_USER_BASE,
+    ldap.SCOPE_SUBTREE,
+    "(uid=%(user)s)"
+)
 AUTH_LDAP_USER_ATTR_MAP = {
     "first_name": "givenName",
     "last_name": "sn",