SQLAlchemy warning

[cphyc]

Whenever I use tangos, the following warning is issued:

/home/ccadiou/codes/tangos/tangos/relation_finding/multi_hop.py:27:
SAWarning: relationship 'HaloLink.halo_to' will copy column halos.id
to column halolink.halo_to_id, which conflicts with relationship(s):
'Halo.all_reverse_links' (copies halos.id to halolink.halo_to_id),
'TimeStep.links_to' (copies halos.id to halolink.halo_to_id). If this
is not the intention, consider if these relationships should be linked
with back_populates, or if viewonly=True should be applied to one or
more if they are read-only. For the less common case that foreign key
constraints are partially overlapping, the orm.foreign() annotation
can be used to isolate the columns that should be written towards.  To
silence this warning, add the parameter
'overlaps="all_reverse_links,links_to"' to the 'HaloLink.halo_to'
relationship. (Background on this error at:
https://sqlalche.me/e/14/qzyx)

This is using the main version of tangos and sqlalchemy.__version__ == "1.4.27".

[apontzen]

Addressed by #165