[MIG] sql_request_abstract: Migration to 17.0

sql_request_abstract/readme/USAGE.md

@@ -0,0 +1,16 @@
+Inherit the model:
+
+``` python
+from odoo import models
+
+class MyModel(models.model)
+    _name = 'my.model'
+    _inherit = ['sql.request.mixin']
+
+    _sql_request_groups_relation = 'my_model_groups_rel'
+
+    _sql_request_users_relation = 'my_model_users_rel'
+```
+
+See implementations in the modules `bi_sql_editor` and `sql_export`.
+(same OCA/reporting-engine repository)