feat(renovate): track oldest maintained k8s

Signed-off-by: kiblik <5609770+kiblik@users.noreply.github.com>

Author: kiblik

.github/renovate.json

@@ -23,14 +23,25 @@
     "commitMessageSuffix": "({{packageFile}})",
     "labels": ["dependencies"]
   }],
+  "customDatasources": {
+    "endoflife-oldest-maintained": {
+      "defaultRegistryUrlTemplate": "https://endoflife.date/api/v1/products/{{packageName}}",
+      "format": "json",
+      "transformTemplates": [
+        "{ \"releases\": [$.result.releases[isMaintained = true]^(<eolFrom)[0].latest.{\"version\": name, \"releaseTimestamp\": date, \"changelogUrl\": link}], \"sourceUrl\": \"https://github.com/kubernetes/kubernetes\", \"homepage\": \"https://kubernetes.io/\" }"
+      ]
+    }
+  },
   "customManagers": [
     {
       "customType": "regex",
       "managerFilePatterns": [
         "/^.github/workflows//"
       ],
       "matchStrings": [
-        "\\w*:\\s[\"']?(?<currentValue>\\S*[^\"']?)[\"']?\\s#\\s*renovate:\\s*datasource=(?<datasource>.*?) depName=(?<depName>.*?)( versioning=(?<versioning>.*?))?\\s"
+        "\\w*:\\s\"(?<currentValue>\\S+)\"\\s#\\s*renovate:\\s*datasource=(?<datasource>.*?) depName=(?<depName>.*?)( versioning=(?<versioning>.*?))?\\s",
+        "\\w*:\\s'(?<currentValue>\\S+)'\\s#\\s*renovate:\\s*datasource=(?<datasource>.*?) depName=(?<depName>.*?)( versioning=(?<versioning>.*?))?\\s",
+        "\\w*:\\s(?<currentValue>\\S+)\\s#\\s*renovate:\\s*datasource=(?<datasource>.*?) depName=(?<depName>.*?)( versioning=(?<versioning>.*?))?\\s"
       ],
       "versioningTemplate": "{{#if versioning}}{{{versioning}}}{{else}}semver{{/if}}"
     }

.github/workflows/k8s-tests.yml

@@ -18,7 +18,7 @@ jobs:
           # are tested (https://kubernetes.io/releases/)
           - k8s: 'v1.34.1' # renovate: datasource=github-releases depName=kubernetes/kubernetes versioning=loose
             os: debian
-          - k8s: 'v1.31.13' # Do not track with renovate as we likely want to rev this manually
+          - k8s: 'v1.31.12' # renovate: datasource=custom.endoflife-oldest-maintained depName=kubernetes
             os: debian
     steps:
       - name: Checkout