Fix/issue 441

[gyurebalint]

Fixes #441

Problem

When a configuration method has a params array parameter (e.g. params string[] ids) and the Args section is omitted entirely from config, the library fails to invoke the method at startup with:
System.ArgumentException: Object of type 'System.DBNull' cannot be converted to type 'System.String[]'.

This happens because:

1. HasImplicitValueWhenNotSpecified does not recognise params parameters as optional — so SelectConfigurationMethod rejects the method entirely when no args are supplied
2. Even if the method were selected, GetImplicitValueForNotSpecifiedKey falls through to return parameter.DefaultValue which is DBNull for params parameters on .NET 10 — causing a crash at invocation

Changes

ConfigurationReader.cs

• Added ParamArrayAttribute check to HasImplicitValueWhenNotSpecified so params parameters are treated as optional during method selection
• Added ParamArrayAttribute check to GetImplicitValueForNotSpecifiedKey to return an empty array of the correct element type instead of DBNull
• Made GetImplicitValueForNotSpecifiedKey
  internal to allow direct unit testing

ConfigurationReaderTests.cs

• Added test asserting that a method with a params string[] parameter is selected when no args are supplied
• Added test asserting that the implicit value for a params string[] parameter is an empty array, not DBNull

Root cause

In .NET 10, params parameters report HasDefaultValue = true but DefaultValue is DBNull — not a valid value for an array type. The fix intercepts params parameters before falling through to return parameter.DefaultValue.

[gyurebalint]

Hi everyone!
Note: I changed GetImplicitValueForNotSpecifiedKey to internal to allow for isolated unit testing of the params logic.
If you'd prefer to keep it private and have this tested strictly through the public API, let me know and I'll adjust the tests.
Any feedback is appreciated.