feat(certificates): cert Customer Contact is multi-contact, auto-filled, sends to all

fp.certificate.contact_partner_id (single 'Customer Contact') becomes
contact_partner_ids (Many2many) — same shape as the partner's Default CoC
Contacts, as requested.

- Auto-populate: at job creation (fp.job cert resolution) + lazy-fill at issue,
  contact_partner_ids = the customer's x_fc_default_coc_contact_ids (ALL).
- Send: action_send_to_customer pre-fills the composer with exactly the cert's
  contact_partner_ids, so the CoC goes to all the defined clients (fallback:
  company).
- Primary: the FIRST contact prints on the CoC + is gated for email; report
  uses contact_partner_ids[:1].
- Gate: requires >=1 Customer Contact + the primary has an email.
- View: many2many_tags.
- Migration 19.0.10.3.0: copies each cert's old single contact into the new M2m,
  drops the orphaned column.

Deployed + verified on entech: migration copied 16 certs, old column dropped,
field is M2m, send pre-fills the cert contacts, CoC report renders. entech-only
part_line_ids preserved.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating_certificates/migrations/19.0.10.3.0/post-migrate.py

@@ -0,0 +1,52 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Nexa Systems Inc.
+# License OPL-1
+"""Migrate the cert's single Customer Contact (Many2one) to a Many2many.
+
+fp.certificate.contact_partner_id (single Many2one column) was renamed to
+contact_partner_ids (Many2many -> res.partner, rel
+fp_certificate_contact_partner_rel) so a cert can carry every contact who
+receives the CoC. Odoo creates the new rel table during the schema-update
+phase but leaves the old column orphaned. Copy each cert's single contact
+into the new M2m (becomes the primary / printed addressee), then drop the
+dead column. Guarded + idempotent.
+"""
+import logging
+
+_logger = logging.getLogger(__name__)
+
+
+def migrate(cr, version):
+    cr.execute("""
+        SELECT 1 FROM information_schema.columns
+         WHERE table_name = 'fp_certificate'
+           AND column_name = 'contact_partner_id'
+    """)
+    if not cr.fetchone():
+        return
+    cr.execute("""
+        SELECT 1 FROM information_schema.tables
+         WHERE table_name = 'fp_certificate_contact_partner_rel'
+    """)
+    if not cr.fetchone():
+        _logger.warning(
+            'fp_certificate_contact_partner_rel missing — skipping cert '
+            'customer-contact migration (rel table not created yet).')
+        return
+    cr.execute("""
+        INSERT INTO fp_certificate_contact_partner_rel (cert_id, partner_id)
+        SELECT c.id, c.contact_partner_id
+          FROM fp_certificate c
+         WHERE c.contact_partner_id IS NOT NULL
+           AND NOT EXISTS (
+               SELECT 1 FROM fp_certificate_contact_partner_rel r
+                WHERE r.cert_id = c.id
+                  AND r.partner_id = c.contact_partner_id)
+    """)
+    moved = cr.rowcount
+    cr.execute(
+        "ALTER TABLE fp_certificate DROP COLUMN IF EXISTS contact_partner_id")
+    _logger.info(
+        'Cert customer-contact migration: copied %s single contact_partner_id '
+        'value(s) into the new contact_partner_ids M2m, dropped old column.',
+        moved)