Release 0.9.2

Release 0.9.2 is a minor release and contains a new mermaid diagram backend, a new model decoration mode for easier development with types and some more features and bugfixes.

• Bug #610: Decorate models appropriately when HierarchicalMachine is passed to add_state (thanks @e0lithic)
• Bug #647: Let may_<trigger> check all parallel states in processing order (thanks @spearsear)
• Bug: HSM.is_state works with parallel states now
• Experimental features:
  • Add model_override to Machine constructor to determine the mode of operation. With model_override=Fale (default), transitions will not override already defined methods on a model just as it did before. For workflows relying on typing, model_override=True will override methods already defined on the model and only those (!). This allows to control which convenience methods shall be assigned to the model and keeps the statically 'assumed' model in sync with its runtime counterpart. Since defining each and every method manually is rather tiresome, transitions.experimental.utils.generate_base_model features a way to convert a machine configuration into a BaseClass with all convenience functions and callbacks.
  • Add transitions.experimental.utils.{add_transitions, event, with_model_definitions, transition} to define trigger methods in a class model for more convenient type checking. add_transitions can be used as a function decorator and is stackable. event returns a placeholder object for attribute assigment. add_transitions and event have the same signature and support transition definition like machine constructors. The function transition can used for better typing and returns a dictionary that can be passed to the utility functions but also to a machine constructor. add_transitions and event require a machine decorated with with_model_definitions. Decorating a machine with_model_definitions implies model_override=True.
• Feature: Add may_trigger to models to check whether transitions can be conducted by trigger name.
• Feature: Add Mermaid diagram backend that returns a mermaid diagram as a string. use_pygraphviz is deprecated in favour for graph_engine which may be pygraphviz (default), graphviz or mermaid.