Make FileLogHandler message creation overrideable
Make FileLogHandler message creation overrideable

Jay-Jay-D/LeanSTP,tomhunter-gh/Lean,devalkeralia/Lean,squideyes/Lean,jameschch/Lean,Phoenix1271/Lean,devalkeralia/Lean,QuantConnect/Lean,mabeale/Lean,squideyes/Lean,andrewhart098/Lean,tomhunter-gh/Lean,andrewhart098/Lean,StefanoRaggi/Lean,StefanoRaggi/Lean,young-zhang/Lean,devalkeralia/Lean,Mendelone/forex_trading,JKarathiya/Lean,AnObfuscator/Lean,StefanoRaggi/Lean,AnshulYADAV007/Lean,QuantConnect/Lean,bizcad/Lean,kaffeebrauer/Lean,andrewhart098/Lean,young-zhang/Lean,JKarathiya/Lean,AlexCatarino/Lean,young-zhang/Lean,tomhunter-gh/Lean,AnshulYADAV007/Lean,bizcad/Lean,Jay-Jay-D/LeanSTP,mabeale/Lean,jameschch/Lean,devalkeralia/Lean,AlexCatarino/Lean,JKarathiya/Lean,AlexCatarino/Lean,kaffeebrauer/Lean,squideyes/Lean,squideyes/Lean,StefanoRaggi/Lean,AnshulYADAV007/Lean,Jay-Jay-D/LeanSTP,Phoenix1271/Lean,Phoenix1271/Lean,StefanoRaggi/Lean,AnObfuscator/Lean,QuantConnect/Lean,kaffeebrauer/Lean,Mendelone/forex_trading,bizcad/Lean,mabeale/Lean,andrewhart098/Lean,AnshulYADAV007/Lean,AlexCatarino/Lean,Jay-Jay-D/LeanSTP,jameschch/Lean,redmeros/Lean,JKarathiya/Lean,Jay-Jay-D/LeanSTP,AnshulYADAV007/Lean,AnObfuscator/Lean,young-zhang/Lean,jameschch/Lean,tomhunter-gh/Lean,mabeale/Lean,kaffeebrauer/Lean,redmeros/Lean,Mendelone/forex_trading,QuantConnect/Lean,redmeros/Lean,Phoenix1271/Lean,AnObfuscator/Lean,kaffeebrauer/Lean,redmeros/Lean,Mendelone/forex_trading,jameschch/Lean,bizcad/Lean