What realmd_tags parameter in sssd config is used for?

I also had a similar question and curiousity. This led me to github and reviewing code for SSSD, however it was the realmd codebase that has the answer.

From https://github.com/freedesktop/realmd/search?q=realmd_tags

        value = realm_ini_config_get (self->pv->config, self->pv->section, "realmd_tags");
        if (value && strstr (value, "manages-system"))
            manages_system = TRUE;
        g_free (value);

There doesn't appear to be any other code that gets the "realmd_tags" configuration. There is code that creates its own realmd_tags, e.g: https://github.com/freedesktop/realmd/blob/63a6453399dddb3d49ec32e6095594ecc322829f/service/realm-sssd-ad.c#L183

    realmd_tags = g_string_new ("");
    if (realm_options_manage_system (options, disco->domain_name))
        g_string_append (realmd_tags, "manages-system ");
    g_string_append (realmd_tags, use_adcli ? "joined-with-adcli " : "joined-with-samba ");

This logic was introduced back in 2012 to handle automatic or one time passwords (and other scenarios), refer to commit: https://github.com/freedesktop/realmd/commit/3a988441e411a8e38f668edf1114397e1726a155