Log error for missing private.conf file

Current Situation

• The Controller (and Agent) will terminate within a few seconds after being started if the <data>/config/private/private.conf file is not present.
• The information about the missing configuration file is logged at DEBUG level which makes it hard for users to identify the root cause why JS7 products terminate immediately after being started.

Desired Behavior

• The information about the missing private.conf configuration file is logged at ERROR level.
• Exit Code 4 is raised if start of the Controller or Agent is unsuccessful due to missing configuration files.

 Maintainer Notes

• The issue is dismissed as it cannot be reproduced with indicated releases.
• Missing settings result in an error logged on Agent start-up like this:

  2025-11-10T12:42:22,580 info  js7.base.system.startup.StartUp - Agent 2.8.2-SNAPSHOT+20251106.0958 (02c7dc8db3129d4b678bb22e4469b45321a44077) · Java 25.0.1 · OpenJDK 64-Bit Server VM 25.0.1+8-alpine-r0 (256MiB) · Linux (Alpine Linux v3.22) · Intel(R) Xeon(R) CPU E5-2630 v4 @ 2.20GHz (8 threads) 31GiB · pid=145 host=agent-2-0-standalone · started at 2025-11-10T12:42:20.838Z Z
  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
  2025-11-10T12:42:23,437 info  js7.base.configutils.Configs - Reading configuration file /var/sos-berlin.com/js7/agent/var_4445/config/private/private.conf
  2025-11-10T12:42:23,438 info  js7.base.configutils.Configs - Reading configuration file /var/sos-berlin.com/js7/agent/var_4445/config/agent.conf
  2025-11-10T12:42:25,293 info  js7.common.pekkohttp.web.session.SessionRegister - Session:1 for User:System: Login (2.8.2-SNAPSHOT ✔) (eternal)
  2025-11-10T12:42:25,470 ERROR js7.common.system.startup.ServiceMain - HTTPS requires a key store: Missing configuration key 'js7.web.https.keystore'
  2025-11-10T12:42:25,472 info  js7.base.log.log4j.Log4j - Shutdown
  2025-11-10T12:42:25,477 End of logging
  

  The above error is reported if the Agent is operated for HTTPS connections and if no settings from the private.conf file are present. Other errors about missing configuration items will be reported if the Agent is configured for HTTP connections.

• Users should verify to either use the ./config/log4j2.xml file provided with Controller/Agent or not to use an individual Log4j2 configuration file.