Chore: Move unittest directory setup onto the shared fixture (#14172)

The unittest side of the suite built its temp directory tree with
tempfile.mkdtemp and a manually enabled override_settings, cleaned up only if
tearDown ran. That is now gone. DirectoriesMixin lives alongside the layout it
bridges and does nothing but hand the paperless_dirs fixture to TestCase
subclasses as self.dirs, so both halves of the suite get the same twelve
settings, the same directory shapes and cleanup owned by tmp_path.

The mixin moves to paperless_testing.dirs rather than staying in the documents
test utilities, because modules in paperless and paperless_mail import it
across the app boundary. The thirty-eight consuming modules change only their
import line; self.dirs.scratch_dir and its siblings keep working.

src/documents/tests/test_double_sided.py

@@ -15,9 +15,9 @@ from documents.data_models import ConsumableDocument
 from documents.data_models import DocumentSource
 from documents.double_sided import STAGING_FILE_NAME
 from documents.double_sided import TIMEOUT_MINUTES
-from documents.tests.utils import DirectoriesMixin
 from documents.tests.utils import DummyProgressManager
 from documents.tests.utils import FileSystemAssertsMixin
+from paperless_testing.dirs import DirectoriesMixin
 
 
 @override_settings(
@@ -29,8 +29,8 @@ class TestDoubleSided(DirectoriesMixin, FileSystemAssertsMixin, TestCase):
 
     def setUp(self) -> None:
         super().setUp()
-        self.dirs.double_sided_dir = self.dirs.consumption_dir / "double-sided"
-        self.dirs.double_sided_dir.mkdir()
+        self.double_sided_dir = self.dirs.consumption_dir / "double-sided"
+        self.double_sided_dir.mkdir()
         self.staging_file = self.dirs.scratch_dir / STAGING_FILE_NAME
 
     def consume_file(self, srcname, dstname: str | Path = "foo.pdf"):
@@ -39,7 +39,7 @@ class TestDoubleSided(DirectoriesMixin, FileSystemAssertsMixin, TestCase):
         destination file does not exist afterwards
         """
         src = self.SAMPLE_DIR / srcname
-        dst = self.dirs.double_sided_dir / dstname
+        dst = self.double_sided_dir / dstname
         dst.parent.mkdir(parents=True, exist_ok=True)
         shutil.copy(src, dst)
         with mock.patch(
@@ -214,31 +214,41 @@ class TestDoubleSided(DirectoriesMixin, FileSystemAssertsMixin, TestCase):
         self.assertIsNotFile(self.staging_file)
         self.assertIsInstance(msg.get("document_id"), int)
 
-    def test_subdirectory_upload(self) -> None:
+    def test_consume_double_sided_in_nested_dir(self) -> None:
         """
         GIVEN:
             - A staging file exists
         WHEN:
-            - A file gets uploaded into foo/bar/double-sided
-              or double-sided/foo/bar
+            - A file is uploaded into foo/bar/double-sided
         THEN:
-            - The collated file gets put into foo/bar
+            - The collated file is placed into foo/bar
         """
-        # TODO: parameterize this instead
-        for path in [
-            Path("foo") / "bar" / "double-sided",
-            Path("double-sided") / "foo" / "bar",
-        ]:
-            with self.subTest(path=str(path)):
-                # Ensure we get fresh directories for each run
-                self.tearDown()
-                self.setUp()
+        self.create_staging_file()
+        self.consume_file(
+            "double-sided-odd.pdf",
+            Path("foo") / "bar" / "double-sided" / "foo.pdf",
+        )
+        self.assertIsFile(
+            self.dirs.consumption_dir / "foo" / "bar" / "foo-collated.pdf",
+        )
 
-                self.create_staging_file()
-                self.consume_file("double-sided-odd.pdf", Path(path) / "foo.pdf")
-                self.assertIsFile(
-                    self.dirs.consumption_dir / "foo" / "bar" / "foo-collated.pdf",
-                )
+    def test_consume_double_sided_with_nested_subdir(self) -> None:
+        """
+        GIVEN:
+            - A staging file exists
+        WHEN:
+            - A file is uploaded into double-sided/foo/bar
+        THEN:
+            - The collated file is placed into foo/bar
+        """
+        self.create_staging_file()
+        self.consume_file(
+            "double-sided-odd.pdf",
+            Path("double-sided") / "foo" / "bar" / "foo.pdf",
+        )
+        self.assertIsFile(
+            self.dirs.consumption_dir / "foo" / "bar" / "foo-collated.pdf",
+        )
 
     @override_settings(CONSUMER_ENABLE_COLLATE_DOUBLE_SIDED=False)
     def test_disabled_double_sided_dir_upload(self) -> None: