Add LTI 1.3 JSON config view

This allows us to create a Developer Key in Canvas via single JSON URL
rather than filling in all these fields manually.

https://canvas.instructure.com/doc/api/file.lti_dev_key_config.html

lti_auth/views.py

@@ -3,6 +3,7 @@
 from django.contrib.auth import authenticate, login
 from django.contrib.auth.decorators import login_required
 from django.contrib.auth.models import Group
+from django.http import JsonResponse
 from django.http.response import HttpResponseRedirect
 from django.shortcuts import get_object_or_404, render
 from django.urls import reverse
@@ -126,6 +127,103 @@ def get_context_data(self, **kwargs):
         return ctx
 
 
+class LTI13JSONConfigView(View):
+    def get(self, **kwargs):
+        json_obj = {
+            "title": "The Best Tool",
+            "description": "1.3 Test Tool used for documentation purposes.",
+            "oidc_initiation_url": "https://your.oidc_initiation_url",
+            "oidc_initiation_urls": {
+                "eu-west-1": "https://your.eu-specific1.oidc_initiation_url",
+                "eu-central-1": "https://your.eu-specific2.oidc_initiation_url"
+            },
+            "target_link_uri": "https://your.target_link_uri",
+            "scopes": [
+                "https://purl.imsglobal.org/spec/lti-ags/scope/lineitem",
+                "https://purl.imsglobal.org/spec/lti-ags/scope/result.readonly"
+            ],
+            "extensions": [
+                {
+                    "domain": "thebesttool.com",
+                    "tool_id": "the-best-tool",
+                    "platform": "canvas.instructure.com",
+                    "privacy_level": "public",
+                    "settings": {
+                        "text": "Launch The Best Tool",
+                        "labels": {
+                            "en": "Launch The Best Tool",
+                            "en-AU": "G'day, Launch The Best Tool",
+                            "es": "Lanzar la mejor herramienta",
+                            "zh-Hans": "启动最佳工具"
+                        },
+                        "icon_url": "https://some.icon.url/tool-level.png",
+                        "selection_height": 800,
+                        "selection_width": 800,
+                        "placements": [
+                            {
+                                "text": "User Navigation Placement",
+                                "icon_url": "https://some.icon.url/my_dashboard.png",
+                                "placement": "user_navigation",
+                                "message_type": "LtiResourceLinkRequest",
+                                "target_link_uri": "https://your.target_link_uri/my_dashboard",
+                                "canvas_icon_class": "icon-lti",
+                                "custom_fields": {
+                                    "foo": "$Canvas.user.id"
+                                }
+                            },
+                            {
+                                "text": "Editor Button Placement",
+                                "icon_url": "https://some.icon.url/editor_tool.png",
+                                "placement": "editor_button",
+                                "message_type": "LtiDeepLinkingRequest",
+                                "target_link_uri": "https://your.target_link_uri/content_selector",
+                                "selection_height": 500,
+                                "selection_width": 500
+                            },
+                            {
+                                "text": "Course Navigation Placement",
+                                "icon_url": "https://static.thenounproject.com/png/131630-200.png",
+                                "placement": "course_navigation",
+                                "message_type": "LtiResourceLinkRequest",
+                                "target_link_uri": "https://your.target_link_uri/launch?placement=course_navigation",
+                                "required_permissions": "manage_calendar",
+                                "selection_height": 500,
+                                "selection_width": 500
+                            }
+                        ]
+                    }
+                }
+            ],
+            "public_jwk": {
+                "kty": "RSA",
+                "alg": "RS256",
+                "e": "AQAB",
+                "kid": "8f796169-0ac4-48a3-a202-fa4f3d814fcd",
+                "n": "nZD7QWmIwj-3N_RZ1qJjX6CdibU87y2l02yMay4KunambalP9g0fU9yZLwLX9WYJINcXZDUf6QeZ-SSbblET-h8Q4OvfSQ7iuu0WqcvBGy8M0qoZ7I-NiChw8dyybMJHgpiP_AyxpCQnp3bQ6829kb3fopbb4cAkOilwVRBYPhRLboXma0cwcllJHPLvMp1oGa7Ad8osmmJhXhM9qdFFASg_OCQdPnYVzp8gOFeOGwlXfSFEgt5vgeU25E-ycUOREcnP7BnMUk7wpwYqlE537LWGOV5z_1Dqcqc9LmN-z4HmNV7b23QZW4_mzKIOY4IqjmnUGgLU9ycFj5YGDCts7Q",
+                "use": "sig"
+            },
+            "custom_fields": {
+                "bar": "$Canvas.user.sisid"
+            }
+        }
+
+        domain = self.request.get_host()
+        launch_url = '%s://%s/%s' % (
+            self.request.scheme, domain,
+            settings.LTI_TOOL_CONFIGURATION['launch_url'])
+
+        ctx = {
+            'domain': domain,
+            'launch_url': launch_url,
+            'title': settings.LTI_TOOL_CONFIGURATION['title'],
+            'description': settings.LTI_TOOL_CONFIGURATION['description'],
+            'embed_icon_url':
+                settings.LTI_TOOL_CONFIGURATION['embed_icon_url'],
+            'embed_tool_id': settings.LTI_TOOL_CONFIGURATION['embed_tool_id'],
+        }
+        return ctx
+
+
 @method_decorator(xframe_options_exempt, name='dispatch')
 class LTILandingPage(TemplateView):
     template_name = 'lti_auth/landing_page.html'