Mannage relations

So far we have created 3 models that have different relationships.
Can we update these relationships?
Yes we can, but only with addRelation and removeRelation functions.
We should note that we should never manually update the relationships created by Lesan with the update or updateMany function. Let the management of the relationships be entirely in Lesan's hands, so that it can always keep them updated and correct.
Let's use addRelation.

• Add Relation function
• Remove Relation function
• What is the relationship really?