[ADD] product_main_seller: Restore OCA addon from original version

- Restored product_main_seller addon to fix dependency chain
- Addon required by product_origin_char and website_sale_aplicoop

[IMP] website_sale_aplicoop: Add demo data configuration to manifest

- Updated __manifest__.py to include demo data files
- Demo data includes partners, suppliers, products, group orders, and sale orders
- Demo data successfully loads during module installation

product_main_seller/hooks.py

@@ -0,0 +1,34 @@
+# Copyright 2024-Today - Sylvain Le GAL (GRAP)
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+import logging
+
+_logger = logging.getLogger(__name__)
+
+
+def pre_init_hook(env):
+    _logger.info("Initializing column main_seller_id on table product_template")
+    cr = env.cr
+    cr.execute("""
+        ALTER TABLE product_template
+        ADD COLUMN IF NOT EXISTS main_seller_id integer;
+        """)
+    cr.execute("""
+        WITH numbered_supplierinfos as (
+            SELECT *, ROW_number() over (
+                partition BY product_tmpl_id
+                ORDER BY sequence, min_qty desc, price
+            ) as row_number
+            FROM product_supplierinfo
+        ),
+
+        first_supplierinfos as (
+            SELECT * from numbered_supplierinfos
+            WHERE row_number = 1
+        )
+
+        UPDATE product_template pt
+        SET main_seller_id = first_supplierinfos.partner_id
+        FROM first_supplierinfos
+        WHERE pt.id = first_supplierinfos.product_tmpl_id;
+        """)