What is equivalent to the FieldDescription class in version 2.0?
In version 1.9 the FieldDescription class was used to query the attributes of a field in a table.
How is this done now?
In version 2.0 all data access has changed. To query the attributes that describe a field in a table you have to make use of the FeatureAttributeDescriptor class.
A vector layer has a FeatureStore, which in turn has a defaultFeatureType, that defines the structure of the feature by means of the FeatureAttributeDescriptor.