fix: canonical and social URLs answered as paths become absolute on the request origin

testing/expect.txt

@@ -49,3 +49,8 @@ report /posts/nope
 200 /google0123.html contains=google-site-verification: google0123.html header=X-Content-Type-Options: nosniff
 404 /unknown0123.html
 404 /robots.txt
+
+# A backend without a site URL answers paths: they become absolute on the
+# request's origin.
+200 /relative contains=<link rel="canonical" href="http://127.0.0.1:
+200 /relative contains=/img/rel.png"> notcontains=content="/img/rel.png"

testing/fixtures/resolve.json

@@ -1,38 +1,158 @@
 {
   "/": {
-    "action": "ok", "status": 200, "url": "https://acme.test/", "locale": "en", "staging": false,
+    "action": "ok",
+    "status": 200,
+    "url": "https://acme.test/",
+    "locale": "en",
+    "staging": false,
     "seo": {
-      "title": "Home | Acme", "description": "Acme home", "canonical": "https://acme.test/",
-      "robots": "index, follow", "x_robots_tag": "index, follow",
-      "og": { "title": "Home | Acme", "description": "Acme home", "image": "https://acme.test/home.png", "url": "https://acme.test/" },
-      "twitter": { "card": "summary_large_image", "site": "@acme" },
+      "title": "Home | Acme",
+      "description": "Acme home",
+      "canonical": "https://acme.test/",
+      "robots": "index, follow",
+      "x_robots_tag": "index, follow",
+      "og": {
+        "title": "Home | Acme",
+        "description": "Acme home",
+        "image": "https://acme.test/home.png",
+        "url": "https://acme.test/"
+      },
+      "twitter": {
+        "card": "summary_large_image",
+        "site": "@acme"
+      },
       "verification": []
     }
   },
   "/about": {
-    "action": "ok", "status": 200, "url": "https://acme.test/about", "locale": "en", "staging": false,
+    "action": "ok",
+    "status": 200,
+    "url": "https://acme.test/about",
+    "locale": "en",
+    "staging": false,
     "seo": {
-      "title": "About us | Acme", "description": "Who we are", "canonical": "https://acme.test/about",
-      "robots": "index, follow, max-image-preview:large", "x_robots_tag": "index, follow, max-image-preview:large",
-      "og": { "title": "About us | Acme", "description": "Who we are", "image": "", "url": "https://acme.test/about" },
-      "twitter": { "card": "summary", "site": "@acme" },
-      "verification": [{ "name": "google-site-verification", "content": "fixture-google-code" }]
+      "title": "About us | Acme",
+      "description": "Who we are",
+      "canonical": "https://acme.test/about",
+      "robots": "index, follow, max-image-preview:large",
+      "x_robots_tag": "index, follow, max-image-preview:large",
+      "og": {
+        "title": "About us | Acme",
+        "description": "Who we are",
+        "image": "",
+        "url": "https://acme.test/about"
+      },
+      "twitter": {
+        "card": "summary",
+        "site": "@acme"
+      },
+      "verification": [
+        {
+          "name": "google-site-verification",
+          "content": "fixture-google-code"
+        }
+      ]
     }
   },
   "/partial": {
-    "action": "ok", "status": 200, "url": "https://acme.test/partial", "locale": "en", "staging": false,
+    "action": "ok",
+    "status": 200,
+    "url": "https://acme.test/partial",
+    "locale": "en",
+    "staging": false,
     "seo": {
-      "title": "", "description": "", "canonical": "https://acme.test/partial",
-      "robots": "", "x_robots_tag": "",
-      "og": { "title": "", "description": "", "image": "", "url": "" },
-      "twitter": { "card": "", "site": "" },
+      "title": "",
+      "description": "",
+      "canonical": "https://acme.test/partial",
+      "robots": "",
+      "x_robots_tag": "",
+      "og": {
+        "title": "",
+        "description": "",
+        "image": "",
+        "url": ""
+      },
+      "twitter": {
+        "card": "",
+        "site": ""
+      },
       "verification": []
     }
   },
-  "/staging": { "action": "not_found", "status": 404, "url": "https://acme.test/staging", "locale": "", "staging": true, "seo": null },
-  "/old-path": { "action": "redirect", "status": 301, "location": "https://acme.test/about", "url": "https://acme.test/old-path", "locale": "", "staging": false, "seo": null },
-  "/old-temp?ref=1": { "action": "redirect", "status": 302, "location": "https://acme.test/about?x=1", "url": "https://acme.test/old-temp?ref=1", "locale": "", "staging": false, "seo": null },
-  "/moved": { "action": "redirect", "status": 301, "location": "https://other.test/x", "url": "https://acme.test/moved", "locale": "", "staging": false, "seo": null },
-  "/gone-path": { "action": "gone", "status": 410, "url": "https://acme.test/gone-path", "locale": "", "staging": false, "seo": null },
-  "/posts/gone-post": { "action": "gone", "status": 410, "url": "https://acme.test/posts/gone-post", "locale": "", "staging": false, "seo": null }
+  "/staging": {
+    "action": "not_found",
+    "status": 404,
+    "url": "https://acme.test/staging",
+    "locale": "",
+    "staging": true,
+    "seo": null
+  },
+  "/old-path": {
+    "action": "redirect",
+    "status": 301,
+    "location": "https://acme.test/about",
+    "url": "https://acme.test/old-path",
+    "locale": "",
+    "staging": false,
+    "seo": null
+  },
+  "/old-temp?ref=1": {
+    "action": "redirect",
+    "status": 302,
+    "location": "https://acme.test/about?x=1",
+    "url": "https://acme.test/old-temp?ref=1",
+    "locale": "",
+    "staging": false,
+    "seo": null
+  },
+  "/moved": {
+    "action": "redirect",
+    "status": 301,
+    "location": "https://other.test/x",
+    "url": "https://acme.test/moved",
+    "locale": "",
+    "staging": false,
+    "seo": null
+  },
+  "/gone-path": {
+    "action": "gone",
+    "status": 410,
+    "url": "https://acme.test/gone-path",
+    "locale": "",
+    "staging": false,
+    "seo": null
+  },
+  "/posts/gone-post": {
+    "action": "gone",
+    "status": 410,
+    "url": "https://acme.test/posts/gone-post",
+    "locale": "",
+    "staging": false,
+    "seo": null
+  },
+  "/relative": {
+    "action": "ok",
+    "status": 200,
+    "url": "/relative",
+    "locale": "en",
+    "staging": false,
+    "seo": {
+      "title": "Relative | Acme",
+      "description": "",
+      "canonical": "/relative",
+      "robots": "",
+      "x_robots_tag": "",
+      "og": {
+        "title": "",
+        "description": "",
+        "image": "/img/rel.png",
+        "url": "/relative"
+      },
+      "twitter": {
+        "card": "",
+        "site": ""
+      },
+      "verification": []
+    }
+  }
 }