[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, 12 insertions, 0 deletions

diff --git a/addons/base_sparse_field/__init__.py b/addons/base_sparse_field/__init__.py
new file mode 100644
index 00000000000..edbaa61c052
--- /dev/null
+++ b/addons/base_sparse_field/__init__.py
@@ -0,0 +1,12 @@
+# -*- coding: utf-8 -*-
+
+from . import models
+from . import tests
+
+def _update_database_schema(cr):
+    # The reflection of fields is done before updating the model's schema,
+    # therefore we first update the schema.
+    cr.execute("""
+        ALTER TABLE ir_model_fields
+        ADD COLUMN serialization_field_id integer REFERENCES ir_model_fields ON DELETE cascade
+    """)