Invalid message contracts and saga data results from non-writable properties

[helenktsai]

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Issue transferred from internal repo

When internal or private access modifiers are apply to message contracts of saga data, this can result in problems, e.g. the XML serializer does not serialize non-writable properties.

Implement a way to indicate to users that they may be causing this problem, e.g. by scanning for invalid properties at startup or runtime, or create a roslyn analyzer to highlight such properties in messages and saga data classes.