Don’t allow broadcasts to be created from JSON

Until we know we’re going to have real users for this, let’s not expose
it.

tests/app/v2/broadcast/test_post_broadcast.py

@@ -51,46 +51,14 @@ def test_valid_post_broadcast_returns_201(
         headers=[('Content-Type', 'application/json'), auth_header],
     )
 
-    assert response.status_code == 201
-
-    response_json = json.loads(response.get_data(as_text=True))
-
-    assert response_json['approved_at'] is None
-    assert response_json['approved_by_id'] == None
-    assert response_json['areas'] == [
-        'Hackney Marshes'
-    ]
-    assert response_json['cancelled_at'] == None
-    assert response_json['cancelled_by_id'] == None
-    assert response_json['content'] == 'This is a test'
-    assert response_json['reference'] == 'abc123'
-    assert response_json['created_at']  # datetime generated by the DB so can’t freeze it
-    assert response_json['created_by_id'] == None
-    assert response_json['finishes_at'] is None
-    assert response_json['id'] == ANY
-    assert response_json['personalisation'] is None
-    assert response_json['service_id'] == str(sample_broadcast_service.id)
-    assert response_json['simple_polygons'] == [[
-        [-0.03817522145265898, 51.557381351011166],
-        [-0.03791399800364216, 51.55758039392131],
-        [-0.030362635618559567, 51.56141279571522],
-        [-0.02986997783677049, 51.56152875195115],
-        [-0.029379069367567606, 51.561405599957745],
-        [-0.023537043373602105, 51.5583323982824],
-        [-0.02328416546450603, 51.55813395976017],
-        [-0.02355422144186266, 51.557933308587664],
-        [-0.0313493058222969, 51.55414241384808],
-        [-0.031840673207720764, 51.55403463730992],
-        [-0.032327132941933706, 51.55416275685022],
-        [-0.037918974384948616, 51.55717594115094],
-        [-0.03817522145265898, 51.557381351011166],
-    ]]
-    assert response_json['starts_at'] is None
-    assert response_json['status'] == 'pending-approval'
-    assert response_json['template_id'] is None
-    assert response_json['template_name'] is None
-    assert response_json['template_version'] is None
-    assert response_json['updated_at'] is None
+    assert response.status_code == 400
+    assert json.loads(response.get_data(as_text=True)) == {
+        'errors': [{
+            'error': 'BadRequestError',
+            'message': 'Content type application/json not supported'
+        }],
+        'status_code': 400,
+    }
 
 
 def test_valid_post_cap_xml_broadcast_returns_201(