Add a Settings > Email previews page showing every branded email with sample data

Renders the real templates every send function uses (claim approved,
membership invoice, invoice reminder) against hand-built placeholder
context -- no real Member/ClubMembership/DuesInvoice row needed, so
nothing here can leak real data. Each card shows the subject line and
toggles between the HTML render (in an iframe, so the email's own
markup can't clash with the page's) and the plain-text body, using
the same bg-steel pill-toggle pattern as the news preview's NL/EN
switch (generalised to .view-toggle-btn, kept .news-lang-btn as an
alias). Admin-only, alongside Club identity in Settings.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ECGMEwrc2k4D8VQuwjstj9

management/email_previews.py

@@ -0,0 +1,92 @@
+"""Sample renders of every branded email this app can send -- the Settings >
+Email previews page (management/templates/management/email_previews.html),
+so a club can see exactly what a member/parent receives without anything
+actually being sent.
+
+Each entry renders the *real* templates the real send functions use (see
+members.services.claims.send_claim_approved_email and
+club.services.invoicing.send_invoice_email/send_reminder_email) against a
+hand-built sample context -- never a real Member/ClubMembership/DuesInvoice
+row, so this needs nothing from the database beyond the current club itself,
+and can't leak anything real. Adding a new branded email later means adding
+one entry here, not touching the view or template.
+"""
+
+import datetime
+from collections.abc import Callable
+from dataclasses import dataclass
+from decimal import Decimal
+from types import SimpleNamespace
+
+from django.template.loader import render_to_string
+from django.utils import timezone
+from django.utils.translation import gettext_lazy as _
+
+
+@dataclass(frozen=True)
+class EmailPreview:
+    key: str
+    label: str
+    description: str
+    subject_template: str
+    text_template: str
+    html_template: str
+    build_context: Callable[..., dict]
+
+
+def _claim_approved_context(club, request):
+    return {
+        "club": club,
+        "child": "Jamie Doe",
+        "parent_first_name": "Alex",
+        "set_password_url": f"https://{club.slug}.rosterchief.app/accounts/password/reset/key/example/",
+        "request": request,
+    }
+
+
+def _dues_invoice_context(club, request, *, overdue):
+    today = timezone.now().date()
+    due_date = today - datetime.timedelta(days=5) if overdue else today + datetime.timedelta(days=14)
+    invoice = SimpleNamespace(number="DUE-2026-00042", amount=Decimal("45.00"), due_date=due_date)
+    membership = SimpleNamespace(season="2026-2027")
+    member = SimpleNamespace(first_name="Jamie")
+    return {"club": club, "invoice": invoice, "membership": membership, "member": member, "request": request}
+
+
+EMAIL_PREVIEWS = [
+    EmailPreview(
+        key="dues_invoice",
+        label=_("Membership invoice"),
+        description=_("Sent when a staff member clicks “Send invoice” for one or more members on the Dues & billing page."),
+        subject_template="club/email/dues_invoice_subject.txt",
+        text_template="club/email/dues_invoice.txt",
+        html_template="club/email/dues_invoice.html",
+        build_context=lambda club, request: _dues_invoice_context(club, request, overdue=False),
+    ),
+    EmailPreview(
+        key="dues_invoice_reminder",
+        label=_("Invoice reminder"),
+        description=_("Sent by the “Send reminders” button, once per invoice that's still unpaid past its due date."),
+        subject_template="club/email/dues_invoice_reminder_subject.txt",
+        text_template="club/email/dues_invoice_reminder.txt",
+        html_template="club/email/dues_invoice_reminder.html",
+        build_context=lambda club, request: _dues_invoice_context(club, request, overdue=True),
+    ),
+    EmailPreview(
+        key="claim_approved",
+        label=_("Parent claim approved"),
+        description=_("Sent when a staff member approves a parent or guardian's claim to a child, from the Parent claims page."),
+        subject_template="members/email/claim_approved_subject.txt",
+        text_template="members/email/claim_approved.txt",
+        html_template="members/email/claim_approved.html",
+        build_context=_claim_approved_context,
+    ),
+]
+
+
+def render_preview(preview: EmailPreview, *, club, request) -> dict:
+    context = preview.build_context(club, request)
+    subject = " ".join(render_to_string(preview.subject_template, context).split())
+    text_body = render_to_string(preview.text_template, context).strip()
+    html_body = render_to_string(preview.html_template, context)
+    return {"subject": subject, "text": text_body, "html": html_body}