🐛 Fixed default theme context

closes #9674

- the collection router had a hardcoded default context "home"
  - this is wrong
- the context array get's automatically filled for the collection
  - if you are serving a page e.g. /page/2/ -> it's "paged"
  - if you are serving / -> it's "home"
    - same for {{body_class}}, it outputs "home-template" on "/"
    - this is the same behaviour as in 1.23.x

core/server/services/routing/CollectionRouter.js

@@ -90,7 +90,7 @@ class CollectionRouter extends ParentRouter {
             filter: this.filter,
             permalinks: this.permalinks.getValue({withUrlOptions: true}),
             type: this.getType(),
-            context: ['home'],
+            context: [],
             frontPageTemplate: 'home',
             templates: this.templates,
             identifier: this.identifier

core/test/unit/services/routing/CollectionRouter_spec.js

@@ -7,6 +7,8 @@ const should = require('should'),
     sandbox = sinon.sandbox.create();
 
 describe('UNIT - services/routing/CollectionRouter', function () {
+    let req, res, next;
+
     describe('instantiate', function () {
         beforeEach(function () {
             sandbox.stub(settingsCache, 'get').withArgs('permalinks').returns('/:slug/');
@@ -16,6 +18,12 @@ describe('UNIT - services/routing/CollectionRouter', function () {
 
             sandbox.spy(CollectionRouter.prototype, 'mountRoute');
             sandbox.spy(CollectionRouter.prototype, 'mountRouter');
+
+            req = sandbox.stub();
+            res = sandbox.stub();
+            next = sandbox.stub();
+
+            res.locals = {};
         });
 
         afterEach(function () {
@@ -117,6 +125,25 @@ describe('UNIT - services/routing/CollectionRouter', function () {
         });
     });
 
+    describe('fn: _prepareIndexContext', function () {
+        it('default', function () {
+            const collectionRouter = new CollectionRouter('/magic/', {permalink: '/:slug/', template: ['home', 'index']});
+
+            collectionRouter._prepareIndexContext(req, res, next);
+
+            next.calledOnce.should.be.true();
+            res.locals.routerOptions.should.eql({
+                filter: 'page:false',
+                permalinks: '/:slug/:options(edit)?/',
+                frontPageTemplate: 'home',
+                templates: ['index', 'home'],
+                identifier: collectionRouter.identifier,
+                context: [],
+                type: 'posts'
+            });
+        });
+    });
+
     describe('permalink in database changes', function () {
         beforeEach(function () {
             sandbox.stub(settingsCache, 'get').withArgs('permalinks').returns('/:slug/');