test(10.1-04): cover the Phase 10.1 extension point Go code

- acme fixture plugin under modules/cabana/testdata/extension (gadgets
  controller, header and form partials, lookup widget, JS and CSS)
- TestPhase101FormExtensionSchema, TestPhase101PartialSchema and
  TestPhase101Toolbar: every widget, partial and toolbar boot rule
- TestPhase101PartialSanitizer: tag, attribute and URL allowlist, escaping,
  per-request trans, size/node/depth caps and the view-model guard
- TestPhase101Assets: exact-key asset hits, revalidation, SPA fall-through,
  boot path checks and ?v= schema URLs
- TestPhase101Actions (PostgreSQL): scoping, fill filter, strict body,
  action permission, error mapping, CSRF header, toolbar and partial routes
- TestPhase101BoardwalkExports: ContentType and SetSecurityHeaders

modules/cabana/testdata/extension/controllers/gadgets/_stats.htm

@@ -0,0 +1,5 @@
+<dl class="summer-stats">
+{{- range .Data.Items -}}
+<div class="summer-stat"><dt class="summer-stat__label">{{ trans .Label }}</dt><dd class="summer-stat__value">{{ .Count }}</dd></div>
+{{- end -}}
+</dl>

modules/cabana/testdata/extension/controllers/gadgets/_summary.htm

@@ -0,0 +1 @@
+<section class="summer-partial" aria-label="{{ trans "acme.demo::lang.gadgets.summary" }}"><p>{{ .Data.Name }}</p></section>

modules/cabana/testdata/extension/controllers/gadgets/config_form.yaml

@@ -0,0 +1,10 @@
+name: acme.demo::lang.gadgets.form
+form: ~/plugins/acme/demo/models/gadget/fields.yaml
+modelClass: Gadget
+defaultRedirect: acme/demo/gadgets
+create:
+    redirect: acme/demo/gadgets/update/:id
+    redirectClose: acme/demo/gadgets
+update:
+    redirect: acme/demo/gadgets
+    redirectClose: acme/demo/gadgets

modules/cabana/testdata/extension/controllers/gadgets/config_list.yaml

@@ -0,0 +1,11 @@
+list: ~/plugins/acme/demo/models/gadget/columns.yaml
+modelClass: Gadget
+title: acme.demo::lang.gadgets.title
+recordUrl: acme/demo/gadgets/update/:id
+recordsPerPage: 20
+showCheckboxes: true
+headerPartial: stats
+toolbar:
+    buttons: [create, delete, recount]
+    search:
+        prompt: backend::lang.list.search_prompt