Diagrams related to OData entities (CAP & ECC)

Builds a small CAP service that uses the framework's reflection API to read an OData entity's elements and associations and emits PlantUML diagram source for it, as a hand-rolled alternative to the OpenAPI/Yuml-based diagram export capire documents. The author contrasts the PlantUML result with the OpenAPI/Yuml diagram, calling it more detailed and giving more control over orientation, colors and links. Part 1 of a two-part series; part 2 covers the same idea for ECC/ABAP.