Merge technical replicates (SRR1 + SRR2 -> SRX)

[millerh1]

Description of feature

The feature I'm hoping for is merging of technical replicates / runs (SRRs) within each sample/experiment (SRX/GSM/etc). I would like the fastq files to be concatenated within each index (SRR1.R1.fq + SRR2.R1.fq -> SRX.R1.fq; SRR1.R2.fq + SRR2.R2.fq -> SRX.R2.fq). Is such a feature possible in the current pipeline? This would be really nice for those who wish to go directly from fetchngs to other nf-core pipelines.

The docs suggest this should be possible (link), but it doesn't seem to be implemented yet.