Refactor media modules. (#15146)

* Removes the `v1` directory from `test.rest.media.v1`.
* Moves the non-REST code from `synapse.rest.media.v1` to `synapse.media`.
* Flatten the `v1` directory from `synapse.rest.media`,  but leave compatiblity
  with 3rd party media repositories and spam checkers.

tests/media/test_base.py

@@ -0,0 +1,38 @@
+# Copyright 2019 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.media._base import get_filename_from_headers
+
+from tests import unittest
+
+
+class GetFileNameFromHeadersTests(unittest.TestCase):
+    # input -> expected result
+    TEST_CASES = {
+        b"inline; filename=abc.txt": "abc.txt",
+        b'inline; filename="azerty"': "azerty",
+        b'inline; filename="aze%20rty"': "aze%20rty",
+        b'inline; filename="aze"rty"': 'aze"rty',
+        b'inline; filename="azer;ty"': "azer;ty",
+        b"inline; filename*=utf-8''foo%C2%A3bar": "foo£bar",
+    }
+
+    def tests(self) -> None:
+        for hdr, expected in self.TEST_CASES.items():
+            res = get_filename_from_headers({b"Content-Disposition": [hdr]})
+            self.assertEqual(
+                res,
+                expected,
+                f"expected output for {hdr!r} to be {expected} but was {res}",
+            )