Fixed masking passwords in a map used for logging in admingui + added warning to documentation

[dmatej]

• This was discussed on GitLab - the bug was reported there
• I added warning about sharing logs into documentation on three appropriate places:
  • To the introduction of the logging documentation
  • To the part about configuring log levels
  • To the list of recommendations in the security guide
• In general passwords are not the only thing which can be misused to compromise some production system. People should be careful when they share logs, especially when they configured more verbose log levels. Internal host names, distinguished names of internal certificates, dumped HTTP communication, TLS negotiations, ....