The MetaContext represents a meta data modification context: the how when used with
modify_with_context, and the what when used with
update_meta_store.
To add a new column/value pair use gda_meta_context_add_column.
To free a MetaContext, created by
MetaContext, use gda_attributes_manager_free.
Since 5.2, you must consider this struct as opaque. Any access to its internal must use public API. Don't try to use
free on a struct that was created manually.