[REF] move support for sparse fields into a separate module (#15070)

This removal has led to a necessary refactoring:
- make the setup of field attributes extensible;
- make the instantiation of custom fields extensible;
- delegate model and field reflection to `ir.model` and `ir.model.fields`;
- move the implementation of sparse and serialized fields to module `base_sparse_field`;

1 files changed, 4 insertions, 0 deletions

diff --git a/addons/base_sparse_field/models/__init__.py b/addons/base_sparse_field/models/__init__.py
new file mode 100644
index 00000000000..37c0f9345cc
--- /dev/null
+++ b/addons/base_sparse_field/models/__init__.py
@@ -0,0 +1,4 @@
+# -*- coding: utf-8 -*-
+
+from . import fields
+from . import models