🐛 FIX: sqlalchemy v2 API warning (#5177)

This commit fixes a warning that is generated by the sqlalchemy:

SAWarning: relationship 'DbLink.input' will copy column db_dbnode.id to column db_dblink.input_id, which conflicts with relationship(s): 'DbNode.inputs_q' (copies db_dbnode.id to db_dblink.input_id), 'DbNode.outputs_q' (copies db_dbnode.id to db_dblink.input_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="inputs_q,outputs_q"' to the 'DbLink.input' relationship.

Note a similar fix was made in aldjemy/aldjemy#199

aiida/backends/sqlalchemy/models/node.py

@@ -156,8 +156,9 @@ class DbLink(Base):
         Integer, ForeignKey('db_dbnode.id', ondelete='CASCADE', deferrable=True, initially='DEFERRED'), index=True
     )
 
-    input = relationship('DbNode', primaryjoin='DbLink.input_id == DbNode.id')
-    output = relationship('DbNode', primaryjoin='DbLink.output_id == DbNode.id')
+    # https://docs.sqlalchemy.org/en/14/errors.html#relationship-x-will-copy-column-q-to-column-p-which-conflicts-with-relationship-s-y
+    input = relationship('DbNode', primaryjoin='DbLink.input_id == DbNode.id', overlaps='inputs_q,outputs_q')
+    output = relationship('DbNode', primaryjoin='DbLink.output_id == DbNode.id', overlaps='inputs_q,outputs_q')
 
     label = Column(String(255), index=True, nullable=False)
     type = Column(String(255), index=True)