ModelicaSystem deprecated, but ModelicaSystemOMC not a replacement #477

When instantiating a ModelicaSystem, I get a deprecation warning to "Please use class ModelicaSystemOMC instead!".

OK, I do that an replace the ModelicaSystem call by ModelicaSystemOMC, only to find out that the API is not compatible at all! The user guide
still advises to use ModelicaSystem. This is quite confusing!

1. Why the deprecation?
2. Please extend the deprecation warning text to offer migration guidance for existing usage (actually, that's valid for all deprecation warnings in general)
3. Please update the user guide appropriately
4. btw, there's typos, this is called "deprecation warning", not "depreciation warning".

I noticed this in the context of trying to find out why loading a package+model with several lmodel values does not work with ModelicaSystem (exit status 3221225781, that should be "dll not found"), but works when run via sendExpression -- I'll try to get an MWE together and report separately. (edit: #478)

Version and OS

• Python Version 3.13.15
• OMPython Version 4.1.0
• OpenModelica Version 1.28.0-dev.836+gca0c61d2c7.cmake
• OS: Windows 11

cc @syntron and @adeas31 who added this in #450