Constrain submission status to fixed list of values

[Cooryd]

Currently there is no logic constraining the status property of a SubmissionEntity to the fixed list of statuses. We should ensure the value being set is one of the following:

{
      INITIAL: 'INITIAL',
      MECA_EXPORT_PENDING: 'MECA_EXPORT_PENDING',
      MECA_EXPORT_FAILED: 'MECA_EXPORT_FAILED',
      MECA_EXPORT_SUCCEEDED: 'MECA_EXPORT_SUCCEEDED',
      MECA_IMPORT_FAILED: 'MECA_IMPORT_FAILED',
      MECA_IMPORT_SUCCEEDED: 'MECA_IMPORT_SUCCEEDED',
}