Fix: reformat long seqs

[joko3ono]

resolve wurmlab/sequenceserver-cloud#415

[tadast]

@joko3ono thanks for looking into this. Could you please add an explanation of what was the issue and how your change fixes the issue to the commit message, and also add some jest unit tests to demonstrate how it works + make sure we don't break it in future?

It's a bit hard to review the changes without context and learning what the bug is from scratch would be very time consuming as I'd have to come up with multiple test scenarios and execute them 😬

[djleite]

things look almost ok

however, there needs to be correct rounding up of the final sequence length. See below that:

• 3,999,920 bp should be 4 Mbp
• 799,920 bp should be 800 Kbp

However...

If we want to show a greater level of precision then we can show to at least 1 decimal place for any value that has units kbp, Mbp and Gbp.

ie
divide these numbers by 1000 and round to the nearest decimal place

• 19,299 bp = 19.3 kbp
• 19,990 bp = 20.0 kbp

divide these numbers by 1000000 and round to the nearest decimal place

• 199,929,999 bp = 199.9 Mbp
• 199,990,000 bp = 200.0 Mbp

[tadast]

@joko3ono also please make sure you add tests for the rounding so that it's not broken in future

[tadast]

Thanks @joko3ono, the code looks good now.

@yannickwurm do you want to test this or happy to merge?