Windows client encodes OS username using ANSI in op_connect -> server 'Cannot transliterate character between character sets'

[samtrion]

Summary

• When Firebird .NET client runs on Windows with a non-ASCII OS username, the server may respond:
  "Invalid connection string\r\nCannot transliterate character between character sets"

Details

• The initial op_connect/DPB packet contains username/runtime strings encoded using the local ANSI code page on Windows.
• The server cannot transliterate those bytes to the server charset and fails before DPB charset negotiation completes.

Suggested fixes

• Encode DPB/op_connect strings in UTF-8 regardless of local ANSI code page, or provide a connection-string flag to force DPB encoding.
• Document the limitation and recommended workarounds for Windows users.