Improve get_declaring_class by avoiding iterations

[GianlucaFicarelli]

Description

In db.utils, improve get_declaring_class by avoiding the iteration over all the registry mappers, to make this function more efficient, since it's called in many endpoints.

Current code:

entitycore/app/db/utils.py

Lines 190 to 204 in 01236ce

	def get_declaring_class[I: Identifiable](
	db_model_class: type[I], column_name: str
	) -> type[I] | None:
	"""Return the class that has a table with project id or None."""
	if not has_project_id_in_columns(db_model_class):
	return None
	declaring_table = db_model_class.__mapper__.columns[column_name].table
	# Iterate all mappers registered with the Base registry
	for mapper in db_model_class.registry.mappers:
	if mapper.local_table is declaring_table:
	return mapper.class_
	return None

Acceptance criteria

• No iterations

[eleftherioszisis]

Improved in #618