(de)serialziation for SQLAlchemy objects

[mik-laj]

Description

We need a common mechanism for deserialization and serialization of SQLAlchemy objects. I recommend marshmallow-sqlalchemy
https://marshmallow-sqlalchemy.readthedocs.io/en/latest/
PR with this change should define all schemas for database objects in accordance with OpenAPI specification

More information about REST API:
#8107

Use case / motivation

This will make writing new endpoints much easier. We will also have one place defining the structure, which will facilitate backward compatibility.

Related Issues

This task is related to
#8110
#8114
#8115
It was divided so that we could do the work with smaller pieces.

[mik-laj]

We will do this when implementing read-only operations for each endpoint. This will allow us to check schema compliance with OpenAPI.