Workflows DSL / Code Editor

In addition to visually designing a workflow, there should be a way to hand-write a workflow using some form of DSL. Could be a simple YAML format or something more advanced using ANTLR4.

The designer would have two views: the visual designer, and the code editor.
Changes in one view are reflected in the other.

Furthermore, there should be a workflow provider that understands this YAML format (similar to the JSON-based one).

Another potential benefit of having a formal DSL is to improve migration from one version of Elsa to the next. The DSL would act as a formal specification to which all (future) versions of Elsa must adhere.

The designer should generate output using this DSL only, decoupling structures internal to Elsa from structures used internal to the designer.

Another possible benefit is that we can now also generate C# workflow classes easily.