implement connection from samplingEvent to a project

[smrgeoinfo]

In the UML model (https://github.com/isamplesorg/metadata/blob/develop/notes/background/SampleMetadataModel.png), sampling event is linked to 'initiative' to represent the activity context of the sampling event-- whether it is a Cruise, field expedition or whatever. Discussion at tech meeting on 2023-06-09 concluded to add a 'project' property on samplingEvent with a string or URI value, so we don't need to delve into the problem of modeling projects (see the example work in https://github.com/isamplesorg/metadata/tree/develop/notes/ProjectMetadata).