Assay name is mandatory in specification but validator does not complain

[nilshoffmann]

https://github.com/HUPO-PSI/mzTab/blob/master/specification_document-releases/2_0-Metabolomics-Release/mzTab_format_specification_2_0-M_release.adoc#6234-assay1-n
states that an assay name is mandatory.
For the https://github.com/HUPO-PSI/mzTab/blob/master/examples/2_0-Metabolomics_Release/MouseLiver_negative.mzTab example, assay names are not set, but validation is successful.

[nilshoffmann]

The current validator implementation does not complain if assay name is not defined. Updating the specification would allow existing implementations to stay the same. The specification should be updated to make the assay name optional, but recommended to be reported, if feasible / helpful for the current use case. The validator could be updated to report an Info level message that reporting an assay name is recommended.