Add db migration and DNS dmarc entries

tests/test_dns_policy.py

@@ -0,0 +1,47 @@
+from app.dns_policy import collect_domain_dns_policy, parse_dmarc_records, parse_spf_records
+
+
+def test_parse_dmarc_record_extracts_policy_tags():
+    parsed, errors = parse_dmarc_records(["v=DMARC1; p=reject; sp=quarantine; pct=50; adkim=s; aspf=r; rua=mailto:d@example.com"])
+
+    assert errors == []
+    assert parsed.p == "reject"
+    assert parsed.sp == "quarantine"
+    assert parsed.pct == 50
+    assert parsed.adkim == "s"
+    assert parsed.rua == "mailto:d@example.com"
+
+
+def test_parse_spf_record_extracts_includes_and_all_mechanism():
+    parsed, errors = parse_spf_records(["v=spf1 include:_spf.google.com include:mailgun.org -all"])
+
+    assert errors == []
+    assert parsed.includes == ["_spf.google.com", "mailgun.org"]
+    assert parsed.all_mechanism == "-all"
+
+
+def test_collect_domain_dns_policy_uses_observed_dkim_selectors():
+    txt_records = {
+        "_dmarc.example.com": ["v=DMARC1; p=reject; pct=100"],
+        "example.com": ["v=spf1 include:_spf.example.net -all"],
+        "s1._domainkey.example.com": ["v=DKIM1; k=rsa; p=abc"],
+    }
+
+    def txt_lookup(name: str) -> list[str]:
+        if name not in txt_records:
+            raise RuntimeError("not found")
+        return txt_records[name]
+
+    policy = collect_domain_dns_policy(
+        "example.com",
+        selectors=["s1"],
+        txt_lookup=txt_lookup,
+        mx_lookup=lambda name: ["10 mail.example.com"],
+    )
+
+    assert policy.dmarc.p == "reject"
+    assert policy.spf.all_mechanism == "-all"
+    assert policy.mx_records == ["10 mail.example.com"]
+    assert policy.dkim[0].selector == "s1"
+    assert policy.dkim[0].record == "v=DKIM1; k=rsa; p=abc"
+    assert policy.errors == []