Y25-103 - scRNA Core pooling documentation

[KatyTaylor]

Describe the Housekeeping
Create some documentation to describe how the scRNA Core pooling works. It's a very complex area and we want to capture the knowledge now, while we have it. The main audience is PSD, to aid future development or maintenance of this area of code, and also Neil, to aid with dealing with support tickets (run through it with him as part of this story).

I suggest putting it as a child page of this one - https://ssg-confluence.internal.sanger.ac.uk/display/PSDPUB/scRNA+Core+Pipeline+Documentation
(up for debate, however, because the above page is meant to be user facing while this is meant to be primarily PSD-facing).

It might also be helpful to reference the Confluence page in a relevant section of the code, to help with discoverability.

The content I'm thinking to cover is:

• cDNA prep submission - 'number of pools' and 'cells per chip well' fields, validation & feasibility check
• point of pooling - algorithm to determine which wells go into which pools
• point of pooling - decision whether to adjust 'number of cells per chip well' or not
  • where Abby's magic table of numbers comes from - attach any relevant spreadsheets from her - may need her input

Main stories to consider:

• Y24-402 - Specify 'no. pools' rather than 'no. samples per pool' in submission sequencescape#4423
• Y24-429 - Check feasibility of cDNA Prep submission sequencescape#4460
• Y24-376 - Pooling algorithm changes #1985
• Y24-384 - Adjust requested pooling strategy to enable two full runs #1992
• Y25-025 - Maintain customer-requested number of repeats (Limber) #2164