DESeq2 module should be able to handle spike-ins

[pinin4fjords]

Is your feature request related to a problem? Please describe

Currently the DESeq module makes no provision for spike-ins. If they were added during the RNA-seq quantification (via use of --additional-fasta), they should be handled in one way or another by DESeq2.

Describe the solution you'd like

Option to dictate one of:

• Strip spikes and run DESeq2 as normal.
• Use the spikes to dictate normalisation factors a la https://support.bioconductor.org/p/9143354/

Failure to do one of those could create artifacts.

Describe alternatives you've considered

No response

Additional context

No response