Add link back to API integration from callbacks

Matches what we do on the API keys and whitelist pages.

app/templates/views/api/callbacks.html

@@ -30,4 +30,8 @@
 	    {% endcall %}
 	  {% endcall %}
 	</div>
+  {{ page_footer(
+    secondary_link=url_for('.api_integration', service_id=current_service.id),
+    secondary_link_text='Back to API integration'
+  ) }}
 {% endblock %}

tests/app/main/views/test_service_settings.py

@@ -11,6 +11,7 @@ from app.utils import email_safe
 from tests import validate_route_permission, service_json
 from tests.conftest import (
     active_user_with_permissions,
+    active_user_no_api_key_permission,
     platform_admin_user,
     normalize_spaces,
     multiple_reply_to_email_addresses,
@@ -1927,6 +1928,41 @@ def test_set_inbound_sms_when_inbound_number_is_not_set(
     assert response.status_code == 200
 
 
+@pytest.mark.parametrize('user, expected_paragraphs', [
+    (active_user_with_permissions, [
+        'Your service can receive text messages sent to 07700900123.',
+        'If you want to turn this feature off, get in touch with the GOV.UK Notify team.',
+        'You can set up callbacks for received text messages on the API integration page.',
+    ]),
+    (active_user_no_api_key_permission, [
+        'Your service can receive text messages sent to 07700900123.',
+        'If you want to turn this feature off, get in touch with the GOV.UK Notify team.',
+    ]),
+])
+def test_set_inbound_sms_when_inbound_number_is_set(
+    client,
+    service_one,
+    mocker,
+    fake_uuid,
+    user,
+    expected_paragraphs,
+):
+    service_one['permissions'] = ['inbound_sms']
+    mocker.patch('app.inbound_number_client.get_inbound_sms_number_for_service', return_value={
+        'data': {'number': '07700900123'}
+    })
+    client.login(user(fake_uuid), mocker, service_one)
+    response = client.get(url_for(
+        'main.service_set_inbound_sms', service_id=SERVICE_ONE_ID
+    ))
+    paragraphs = BeautifulSoup(response.data.decode('utf-8'), 'html.parser').select('main p')
+
+    assert len(paragraphs) == len(expected_paragraphs)
+
+    for index, p in enumerate(expected_paragraphs):
+        assert normalize_spaces(paragraphs[index].text) == p
+
+
 def test_empty_letter_contact_block_returns_error(
     logged_in_client,
     service_one,

tests/conftest.py

@@ -1236,6 +1236,31 @@ def active_user_manage_template_permission(fake_uuid):
     return user
 
 
+@pytest.fixture
+def active_user_no_api_key_permission(fake_uuid):
+    from app.notify_client.user_api_client import User
+
+    user_data = {
+        'id': fake_uuid,
+        'name': 'Test User With Permissions',
+        'password': 'somepassword',
+        'password_changed_at': str(datetime.utcnow()),
+        'email_address': 'test@user.gov.uk',
+        'mobile_number': '07700 900762',
+        'state': 'active',
+        'failed_login_count': 0,
+        'permissions': {SERVICE_ONE_ID: [
+            'manage_templates',
+            'manage_settings',
+            'view_activity',
+        ]},
+        'platform_admin': False,
+        'auth_type': 'sms_auth'
+    }
+    user = User(user_data)
+    return user
+
+
 @pytest.fixture(scope='function')
 def api_user_locked(fake_uuid):
     from app.notify_client.user_api_client import User