intrastat_base: use fiscal position, following suggestion on issue #110

Improve layout of config page

intrastat_base/models/account_fiscal_position.py

@@ -0,0 +1,30 @@
+# Copyright 2020 Akretion France (http://www.akretion.com/)
+# @author: <alexis.delattre@akretion.com>
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+from odoo import fields, models
+
+
+class AccountFiscalPosition(models.Model):
+    _inherit = "account.fiscal.position"
+
+    intrastat = fields.Boolean(
+        string="Intrastat",
+        help="Set to True if the invoices with this fiscal position should "
+        "be taken into account for the generation of the intrastat reports."
+    )
+
+
+class AccountFiscalPositionTemplate(models.Model):
+    _inherit = "account.fiscal.position.template"
+
+    intrastat = fields.Boolean(string="Intrastat")
+
+
+class AccountChartTemplate(models.Model):
+    _inherit = "account.chart.template"
+
+    def _get_fp_vals(self, company, position):
+        vals = super()._get_fp_vals(company, position)
+        vals['intrastat'] = position.intrastat
+        return vals