add endpoint for verifying webauthn login

with sms and email auth the api handles verifying logins in the
`/<user_id>/verify/code` endpoint, when it checks the code is valid etc.
The admin app has already done this for webauthn logins, but we still
need an API endpoint so that we can set up the user's db entry to have
a new logged in timestamp, a new session id (this is important for
logging out other browser sessions), etc.

Also, we need to be able to make sure that the user's max login count
isn't exceeded. If it's exceeded, we shouldn't let them log in even with
a valid webauthn check.

This endpoint is a POST where the admin passes in a json dict with key
"succesful" being True or False. True sets up the db stuff as mentioned.
False just increments the failed login count.

tests/app/user/test_rest.py

@@ -1,6 +1,6 @@
+import uuid
 import json
 from datetime import datetime
-from uuid import UUID
 
 import mock
 import pytest
@@ -278,7 +278,7 @@ def test_post_user_attribute(client, sample_user, user_attribute, user_value):
         },
         recipient='newuser@mail.com', reply_to_text='notify@gov.uk',
         service=mock.ANY,
-        template_id=UUID('c73f1d71-4049-46d5-a647-d013bdeca3f0'), template_version=1
+        template_id=uuid.UUID('c73f1d71-4049-46d5-a647-d013bdeca3f0'), template_version=1
     )),
     ('mobile_number', '+4407700900460', dict(
         api_key_id=None, key_type='normal', notification_type='sms',
@@ -287,7 +287,7 @@ def test_post_user_attribute(client, sample_user, user_attribute, user_value):
             'email address': 'notify@digital.cabinet-office.gov.uk'
         },
         recipient='+4407700900460', reply_to_text='testing', service=mock.ANY,
-        template_id=UUID('8a31520f-4751-4789-8ea1-fe54496725eb'), template_version=1
+        template_id=uuid.UUID('8a31520f-4751-4789-8ea1-fe54496725eb'), template_version=1
     ))
 ])
 def test_post_user_attribute_with_updated_by(
@@ -1149,3 +1149,68 @@ def test_get_sms_reply_to_for_notify_service(team_member_mobile_edit_template, n
     reply_to = get_sms_reply_to_for_notify_service(number, team_member_mobile_edit_template)
     assert reply_to == current_app.config['NOTIFY_INTERNATIONAL_SMS_SENDER'] \
         if expected_reply_to == 'notify_international_sender' else current_app.config['FROM_NUMBER']
+
+
+@freeze_time('2020-01-01 11:00')
+def test_verify_webauthn_login_resets_login_if_succesful(admin_request, sample_user):
+    sample_user.failed_login_count = 1
+
+    assert sample_user.current_session_id is None
+    assert sample_user.logged_in_at is None
+
+    admin_request.post(
+        'user.verify_webauthn_login_for_user',
+        user_id=sample_user.id,
+        _data={'successful': True},
+        _expected_status=204
+    )
+
+    assert sample_user.current_session_id is not None
+    assert sample_user.failed_login_count == 0
+    assert sample_user.logged_in_at == datetime(2020, 1, 1, 11, 0)
+
+
+def test_verify_webauthn_login_returns_204_when_not_successful(admin_request, sample_user):
+    # when unsuccessful this endpoint is used to bump the failed count. the endpoint still worked
+    # properly so should return 204 (no content).
+    sample_user.failed_login_count = 1
+
+    assert sample_user.current_session_id is None
+    assert sample_user.logged_in_at is None
+
+    admin_request.post(
+        'user.verify_webauthn_login_for_user',
+        user_id=sample_user.id,
+        _data={'successful': False},
+        _expected_status=204
+    )
+
+    assert sample_user.current_session_id is None
+    assert sample_user.failed_login_count == 2
+    assert sample_user.logged_in_at is None
+
+
+def test_verify_webauthn_login_raises_403_if_max_login_count_exceeded(admin_request, sample_user):
+    # when unsuccessful this endpoint is used to bump the failed count. the endpoint still worked
+    # properly so should return 204 (no content).
+    sample_user.failed_login_count = 10
+
+    admin_request.post(
+        'user.verify_webauthn_login_for_user',
+        user_id=sample_user.id,
+        _data={'successful': True},
+        _expected_status=403
+    )
+
+    assert sample_user.current_session_id is None
+    assert sample_user.failed_login_count == 10
+    assert sample_user.logged_in_at is None
+
+
+def test_verify_webauthn_login_raises_400_if_schema_invalid(admin_request):
+    admin_request.post(
+        'user.verify_webauthn_login_for_user',
+        user_id=uuid.uuid4(),
+        _data={'successful': 'True'},
+        _expected_status=400
+    )