Add opensearch declaration (#1058)

* feat: Add opensearch declaration

* cleanup

---------

Co-authored-by: Johannes Zorn <johannes.zorn@zollsoft.com>
Co-authored-by: Sascha Ißbrücker <sascha.issbruecker@gmail.com>

bookmarks/tests/test_opensearch_view.py

@@ -0,0 +1,25 @@
+from django.test import TestCase
+from django.urls import reverse
+
+
+class OpenSearchViewTestCase(TestCase):
+
+    def test_opensearch_configuration(self):
+        response = self.client.get(reverse("linkding:opensearch"))
+        self.assertEqual(response.status_code, 200)
+        self.assertEqual(
+            response["content-type"], "application/opensearchdescription+xml"
+        )
+
+        base_url = "http://testserver"
+        expected_content = f"""
+            <OpenSearchDescription xmlns="http://a9.com/-/spec/opensearch/1.1/" xmlns:moz="http://www.mozilla.org/2006/browser/search/">
+                <ShortName>Linkding</ShortName>
+                <Description>Linkding</Description>
+                <InputEncoding>UTF-8</InputEncoding>
+                <Image width="16" height="16" type="image/x-icon">{base_url}/static/favicon.ico</Image>
+                <Url type="text/html" template="{base_url}/bookmarks?client=opensearch&amp;q={{searchTerms}}"/>
+            </OpenSearchDescription>
+        """
+        content = response.content.decode()
+        self.assertXMLEqual(content, expected_content)