Add TileLayer.tms

The convention is to call TMS a slippy map tile format with "reverted"
Y coordinates (i.e. starting from South instead of from North).

fix umap-project/umap#453

leaflet_storage/migrations/0004_tilelayer_tms.py

@@ -0,0 +1,20 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11 on 2017-04-26 12:58
+from __future__ import unicode_literals
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('leaflet_storage', '0003_auto_20160910_0624'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='tilelayer',
+            name='tms',
+            field=models.BooleanField(default=False),
+        ),
+    ]

leaflet_storage/models.py

@@ -73,6 +73,8 @@ class TileLayer(NamedModel):
         null=True,
         help_text=_('Order of the tilelayers in the edit box')
     )
+    # See https://wiki.openstreetmap.org/wiki/TMS#The_Y_coordinate
+    tms = models.BooleanField(default=False)
 
     @property
     def json(self):

tests/test_tilelayer.py

@@ -0,0 +1,21 @@
+import pytest
+
+from .base import TileLayerFactory
+
+pytestmark = pytest.mark.django_db
+
+
+def test_tilelayer_json():
+    tilelayer = TileLayerFactory(attribution='Attribution', maxZoom=19,
+                                 minZoom=0, name='Name', rank=1, tms=True,
+                                 url_template='http://{s}.x.fr/{z}/{x}/{y}')
+    assert tilelayer.json == {
+        'attribution': 'Attribution',
+        'id': tilelayer.id,
+        'maxZoom': 19,
+        'minZoom': 0,
+        'name': 'Name',
+        'rank': 1,
+        'tms': True,
+        'url_template': 'http://{s}.x.fr/{z}/{x}/{y}'
+    }