🍱 Add an example using wetlab.Biosample to the registries guide

[falexwolf]

Given how common this is, it'd be nice to create a few biosamples in the toy data. Or maybe do it with ULabels. 🤔

Something along these lines:

import wetlab as wl
from django.db.models import F

wl.Biosample.filter(
    created_at__gt="2024-12-01"
).annotate(
    fcs_file__key=F('artifacts__key')
).filter(
    artifacts__key__endswith='.fcs'
).df()

It might also be that this doesn't work entirely yet because of the annotate() call.

Also adding a more complex example

import pandas as pd
from django.db.models import F, Subquery, OuterRef

# First, create a subquery to get only .fcs artifacts
fcs_artifacts = (
    Biosample.artifacts.through.objects
    .filter(artifact__key__endswith='.fcs')
    .filter(biosample=OuterRef('pk'))
    .values('artifact__key')
)

# Now use this subquery in the main query
queryset = (
    wl.Biosample.filter(
    created_at__gt="2024-12-01"
).annotate(
artifacts__key=Subquery(fcs_artifacts[:1])
).filter(artifacts__key__isnull=False)
)

# Convert to DataFrame with all fields
df = pd.DataFrame.from_records(
    queryset.values()
)