Ümläüts in identifiers fail config parsing with "EOF"

[Al2Klimov]

Describe the bug

[2026-06-01 13:57:09 +0000] critical/config: Error: syntax error, unexpected end of file, expecting T_IDENTIFIER
Location: in /etc/icinga2/conf.d/services.conf: 39:26-39:26
/etc/icinga2/conf.d/services.conf(37):   check_command = "ping6"
/etc/icinga2/conf.d/services.conf(38):
/etc/icinga2/conf.d/services.conf(39):   assign where host.vars.äddress6
                                                                ^
/etc/icinga2/conf.d/services.conf(40): }
/etc/icinga2/conf.d/services.conf(41):
[2026-06-01 13:57:09 +0000] critical/cli: Config validation failed. Re-run with 'icinga2 daemon -C' after fixing the config.

To Reproduce

1. Make a service apply rule with assign where host.vars.äddress6
2. Run icinga2 daemon -C

Expected behavior

Error message says what's actually wrong, not "end of file" which is not true.

Additional context

I was testing Icinga/icingaweb2-module-director#2972.

[Al2Klimov]

Workaround

In Director, use host.vars["databäses"] in assign rules.