Enhance substitution handling in ir.actions.report with value_type support

• Refactor converter building functionality for improved maintainability.

• Added substitution_mixin.py with the new SubstitutionMixin abstract model.

• Updated ir.actions.report to inherit from SubstitutionMixin and implement _get_template to return redner_tmpl_id.

• Updated mail.template to inherit from SubstitutionMixin, replacing its simpler action_get_substitutions with the mixin's implementation, and added _get_template.

models/ir_actions_report.py

@@ -36,7 +36,8 @@
     file.
     """
 
-    _inherit = "ir.actions.report"
+    _inherit = ["ir.actions.report", "substitution.mixin"]
+    _name = "ir.actions.report"
 
     @api.constrains("redner_filetype", "report_type")
     def _check_redner_filetype(self):
@@ -111,30 +112,6 @@
             filetype = rec.redner_filetype
             rec.is_redner_native_format = fmt.get_format(filetype).native
 
-    def action_get_substitutions(self):
-        """Call by: action button `Get Substitutions from Redner Report`"""
-        self.ensure_one()
-
-        if self.redner_tmpl_id:
-            keywords = self.redner_tmpl_id.get_keywords()
-
-            # Get current substitutions
-            subs = self.substitution_ids.mapped("keyword") or []
-            values = []
-            for key in keywords:
-                # check to avoid duplicate keys
-                if key not in subs:
-                    values.append((0, 0, {"keyword": key}))
-            self.write({"substitution_ids": values})
-
-            # remove obsolete keywords in substitutions model
-            if len(self.substitution_ids) > len(keywords):
-                deprecated_keys = self.substitution_ids.filtered(
-                    lambda s: s.keyword not in keywords
-                )
-                if len(deprecated_keys) > 0:
-                    deprecated_keys.unlink()
-
     def get_report_metadata(self):
         self.ensure_one()
 
@@ -239,3 +216,19 @@
                 attachment_vals["name"],
             )
         return buffer
+
+    # -------------------------------------------------------------------------
+    # MIXIN METHODS
+    # -------------------------------------------------------------------------
+
+    def _get_substitution_field(self):
+        """Return the substitution field name for ir.actions.report."""
+        return "substitution_ids"
+
+    def _get_template(self):
+        """Get template for ir.actions.report."""
+        return self.redner_tmpl_id
+
+    def _get_substitutions(self):
+        """Get substitutions for ir.actions.report."""
+        return self.substitution_ids