User Macros cannot make use of the default parameter

When creating a user macro, there is no support for specifying use of the default parameter – <ac:default-parameter> in storage format.

When defining the macro parameters, parsing of parameters requires that the macro parameter have a name, otherwise the parameter is ignored (with the log warning of "Skipping undefined parameter for macro <macroName>"). However, the default parameter has no name.

This is of particular concern to users upgrading from 3.5 to 4.x, where their user macros will be migrated to use <ac:default-parameter>, yet it cannot be referenced as a legitimate user macro parameter by the macro browser.