Add application property to switch on storage of error messages

[kevinwallimann]

Background

In #819, a new feature was added that stores error messages of failed runs in the database. Since the database could grow significantly because of this feature, it should only be enabled after a regular cleanup of the job instances table has been scheduled (see #828 and https://github.com/absa-group/ansible_projects-hyperdrive_automated_deployment/issues/17)

Feature

• Add a new boolean application property sparkYarnSink.saveDiagnostics should be added, default value: false
• If the property is set to true, save the diagnostics, otherwise don't