check x_spi_platform_code

[jen-thomas]

The field x_spi_platform_code in ````datapackage.jsonis created from the ship's ID, expedition code and the parent DOI suffix of the dataset, eg. UBXH3_ACE_3897169```

The parent DOI suffix is also used in the directory name, but nowhere else in the FD package.

It would be useful to check that this DOI suffix matches in both places.

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Example of parent DOI: https://doi.org/10.5281/zenodo.3367283 is the parent DOI of all the versions of this dataset. Using the parent DOI will always resolve to the latest version in the browser.