Collect all diagnostics available from SQLGetDiagRec as nested exceptions

[mloskot]

The recent_error calls SQLGetDiagRec in a loop already:

nanodbc/nanodbc/nanodbc.cpp

Lines 391 to 394 in 9b9e819

	do
	{
	NANODBC_CALL_RC(
	NANODBC_FUNC(SQLGetDiagRec),

nanodbc/nanodbc/nanodbc.cpp

Line 441 in 9b9e819

} while (rc != SQL_NO_DATA);

because there sometimes is a list of available diagnostics, but it currently captures the last one only.

A desired enhancement is to collect all available diagnostics as perhaps nested or linked exceptions.
For example, faciliated database_error with std::nested_exception.

References

• test: Fix test_error with correct SQL State and native code #308
• recent_error utility function #310

[thebyohazard]

As mentioned in #361, I also wish to see all diagnostics. I am using MSSQL Server 2008 + Ubuntu Focal + unixodbc + MSSQL ODBC driver 17 for Linux + nanodbc. There is a section of code at the end of recent_error as follows:

// NOTE: unixODBC using PostgreSQL and SQLite drivers crash if you call SQLGetDiagRec()
// more than once. So as a (terrible but the best possible) workaround just exit
// this loop early on non-Windows systems.
#ifndef _MSC_VER
        break;
#endif

When I commented that out, I see all of the print statements from my stored procedure as desired because it appends them all together. For my purposes, this is sufficient and I don't need it in a nested exception.

So maybe there needs to be a more elaborate check as to what type of driver is being used if that is possible rather than just removing other diagnostics for all non-windows systems.