[ZTF] Endpoint to bulk download SSO data

[JulienPeloton]

This PR adds a new route for the ZTF API to download all SSO lightcurve in once.

curl -H "Content-Type: application/json" -X POST \
    -d '{"output-format":"parquet"}' \
    https://api.ztf.fink-portal.org/api/v1/ssobulk \
    -o sso_fink_ztf_lc.parquet

It will download a 2GB parquet file on disk. The output-format You can choose CSV, JSON, etc. as well for the output if you prefer, but that will be a bigger file. Columns should be self-explanatory, except the column residuals which is the difference between lightcurve and the sHG1G2 model (Carry et al 2024). This file contains only the SSO that pass criteria for model fitting (at least 50 measurements, all bands). That's about 180k objects.

This PR is a result of the LSST SSSC Sprint 2026 at Queens University, Belfast.

Todo:

• update the file on HDFS
• Add schema (GET?)