Initial Sonargraph model for OASP4j (fixes #125)

[tlueecke]

This PR provides an initial version of a sonargraph model. Since we seem to have some architecture violations in the sample, it also includes virtual refactoring proposals for fixing those.

[hohwille]

The config is specific for the restaurant app which is deprecated and will be deleted soon. Further we have modeled the same with SonarQube (via ArchitecturalConstraint rules). We should figure out what are the differences and added values of SonarGraph. IMHO with the planned extension to SonarQube this will all be superseded. Should we really add this then???

[hohwille]

peanuts but OASP indentation is 2 spaces not 4.

[tlueecke]

@hohwille I would definitely not enforce usage of Sonargraph - it being a commercial product being one of the main reasons. However, Sonargraph has a different approach as far as I can see in that you define your architecture not by negation of prohibited dependencies. This makes the architecture IMHO more understandable and easier to maintain - especially for larger projects.

However, recommending to use SonarQube as the default would also be for me the way to go. This contribution was rather thought of as an opt-in feature for those probjects like mine, where the customer uses Sonargraph as a the standard for monitoring the architecture.

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