Added completion API logic for worklists + Fixed pydantic validation for worklists group and completion modifications

• Added logic to "close" worklist items when "Complete" is included in the request.
  • Form instance substitutes the current date/time for the complete value, which is then persisted to the model.
• Fixed errors in clean method related to initialization of errors for validation rules.
• Modified dicomweb rest view to inherit the worklist rest view