Metadata has no keyword constructor, and AWESIO_VERSION is not public #49

A writer that builds a SystemDefinition from a model (KiteModels' system_definition for KPS3/KPS4, OpenSourceAWE/KiteModels.jl#327) has to call Metadata with all seven fields positionally, and to fill awesIO_version it reads KiteGeometry.AWESIO_VERSION, which is neither exported nor public. It also has to build the definition twice to fill connectivity_sha, since that is computed from the finished tables.

What I would do: a keyword constructor Metadata(; name, description="", note="", n_points, ...) that defaults awesIO_version to AWESIO_VERSION and schema to "structure_schema.yml", and a SystemDefinition keyword path that fills connectivity_sha from its own tables when none is given, as placed_definition already does internally. Then KiteModels drops its literals and the double build.