Support mappers

[lyz-code]

Description

It would be nice if the repositories could load a schema to understand the relationship between entities.

In this schema we could define the following relationships:

• One to one
• One to many
• Many to many

In a way that when we .get an object we get the option to load the mappers, and if they are, the repo will get the required objects and load them in the specified attribute.

Possible Solution

At repo initialization, a schema attribute is set with the desired relationships.

Then we will need to decide how it affects the different base methods.

Additional context

Related Issue

[lyz-code]

Check how ODMantic has solved it

[lyz-code]

Also remove the skip of the test_repo_can_search_in_list_of_str_attribute test

[lyz-code]

I've started working on the feat/add-relationships branch in case anyone want's to follow this path

[lyz-code]

Check how ormar has solved it