handle serialization of secrets sent from the CLI (#985)

This normalizes the SecretData serialization from the client to address #981.

When serializing objects sent to the service with secrets, we would turn it into a SecretData

We use SecretData to convert this:
`{"auth": {"user": "A", "personal_access_token": "B"}}`
to this:
`"auth": { "secret": { "url": "https://KEYVAULT-URL" }}`

Currently, in the case we have a SecretData we've not yet saved, the serialized form looks like this:
`{"auth": { "secret": {"user": "A", "personal_access_token": "B"}}}`

This PR simplifies the client side serialization to this:
`{"auth": {"user": "A", "personal_access_token": "B"}}`

src/cli/tests/test_serialize.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python
+#
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+import unittest
+
+from onefuzztypes.models import TeamsTemplate
+
+from onefuzz.backend import serialize
+
+
+class TestSerialize(unittest.TestCase):
+    def test_cli_backend_secret_data_serialize(self) -> None:
+        base = TeamsTemplate(url="https://contoso.com")
+        converted = serialize(base)
+        self.assertEqual(converted, {"url": "https://contoso.com"})
+
+
+if __name__ == "__main__":
+    unittest.main()