Attach proof of cover to a warranty

A provider lookup answers whether a unit is covered. It does not produce the
invoice or the extended-warranty certificate, and a manually entered warranty
had nowhere to keep one - so the proof stayed in somebody's mailbox until they
left.

Two columns rather than one: the served URL of the stored document, and the
name the vendor sent it under, because "Dell invoice 4471.pdf" is what a person
recognises a year later and "warranty-12.pdf" is not. The download route sends
the original name back.

Authenticated in both directions, unlike an asset photo: an invoice carries
pricing and a service tag. One document per warranty, replacing any prior
extension so a re-upload as .pdf does not leave the old .png behind claiming to
be current. Capped at 25MB - a certificate is a document, not a disk image.

Office formats are allowed because purchase records genuinely arrive as .msg
and .xlsx, not only as PDFs.

tests/test_plugins/test_warranty_proof.py

@@ -0,0 +1,110 @@
+"""Tests for the warranty proof-of-cover document.
+
+A provider lookup answers whether a unit is covered; it does not produce the
+invoice or the extended-warranty certificate. Those had nowhere to live, so
+they stayed in somebody's mailbox. These pin the parts that are easy to get
+wrong: the document is authenticated on the way out, one per warranty, and the
+vendor's own filename survives so a download is recognisable.
+"""
+
+import io
+
+from plugins.warranty.models import Warranty
+
+
+def _warranty(db, vendor='Dell'):
+    w = Warranty(vendor=vendor, servicetag='ABC123', provider='manual')
+    db.session.add(w)
+    db.session.commit()
+    return w
+
+
+def test_upload_sets_url_and_keeps_the_original_filename(client, db, auth_headers):
+    w = _warranty(db)
+
+    response = client.post(f'/api/warranty/{w.warrantyid}/proof',
+                           data={'file': (io.BytesIO(b'%PDF-1.4 invoice'),
+                                          'Dell invoice 4471.pdf')},
+                           content_type='multipart/form-data',
+                           headers=auth_headers)
+
+    assert response.status_code == 200, response.get_json()
+    body = response.get_json()['data']
+    assert body['proofurl'] == f'/api/warranty/proof/warranty-{w.warrantyid}.pdf'
+    assert body['prooffilename'] == 'Dell invoice 4471.pdf'
+
+
+def test_download_needs_a_token_and_uses_the_vendor_filename(client, db, auth_headers):
+    """An invoice carries pricing and a service tag - not open like an asset photo."""
+    w = _warranty(db)
+    client.post(f'/api/warranty/{w.warrantyid}/proof',
+                data={'file': (io.BytesIO(b'%PDF-1.4 invoice'), 'Dell invoice 4471.pdf')},
+                content_type='multipart/form-data', headers=auth_headers)
+    path = f'/api/warranty/proof/warranty-{w.warrantyid}.pdf'
+
+    assert client.get(path).status_code == 401
+
+    authed = client.get(path, headers=auth_headers)
+    assert authed.status_code == 200
+    assert authed.data == b'%PDF-1.4 invoice'
+    disposition = authed.headers.get('Content-Disposition', '')
+    assert 'attachment' in disposition
+    assert 'Dell invoice 4471.pdf' in disposition
+
+
+def test_rejects_an_unsupported_type(client, db, auth_headers):
+    w = _warranty(db)
+
+    response = client.post(f'/api/warranty/{w.warrantyid}/proof',
+                           data={'file': (io.BytesIO(b'MZ'), 'setup.exe')},
+                           content_type='multipart/form-data',
+                           headers=auth_headers)
+
+    assert response.status_code == 400
+    assert 'Unsupported document type' in response.get_data(as_text=True)
+
+
+def test_rejects_an_oversize_document(client, db, auth_headers, monkeypatch):
+    from plugins.warranty.api import routes
+    monkeypatch.setattr(routes, 'MAX_PROOF_BYTES', 512)
+    w = _warranty(db)
+
+    response = client.post(f'/api/warranty/{w.warrantyid}/proof',
+                           data={'file': (io.BytesIO(b'x' * 2048), 'scan.pdf')},
+                           content_type='multipart/form-data',
+                           headers=auth_headers)
+
+    assert response.status_code == 400
+    assert 'the limit is' in response.get_data(as_text=True)
+
+
+def test_replacing_keeps_one_document_per_warranty(client, db, auth_headers):
+    import glob
+    import os
+    from flask import current_app
+    w = _warranty(db)
+
+    client.post(f'/api/warranty/{w.warrantyid}/proof',
+                data={'file': (io.BytesIO(b'first'), 'scan.png')},
+                content_type='multipart/form-data', headers=auth_headers)
+    client.post(f'/api/warranty/{w.warrantyid}/proof',
+                data={'file': (io.BytesIO(b'%PDF second'), 'invoice.pdf')},
+                content_type='multipart/form-data', headers=auth_headers)
+
+    proofdir = os.path.join(current_app.instance_path, 'warrantyproofs')
+    files = glob.glob(os.path.join(proofdir, f'warranty-{w.warrantyid}.*'))
+    assert len(files) == 1 and files[0].endswith('.pdf')
+
+
+def test_removing_clears_both_columns(client, db, auth_headers):
+    w = _warranty(db)
+    client.post(f'/api/warranty/{w.warrantyid}/proof',
+                data={'file': (io.BytesIO(b'%PDF'), 'invoice.pdf')},
+                content_type='multipart/form-data', headers=auth_headers)
+
+    response = client.delete(f'/api/warranty/{w.warrantyid}/proof',
+                             headers=auth_headers)
+
+    body = response.get_json()['data']
+    assert body['proofurl'] is None
+    assert body['prooffilename'] is None