feat(11.1-04): add the Backend section, the remaining Services pages and the concept map links

- docs/backend: admin controllers, forms, lists and filters, relation
  manager, users and permissions, settings, partials and widgets, admin SPA
- docs/services: storage, outbound HTTP, realtime, Web Push, search, parity
  testing and the Frontend and AJAX (not provided) page
- Examples for cabana (with testdata/docs YAML), fetchguard, lighthouse and
  its centrifugo driver, flare, beachcomber and typesense, tide; lighthouse
  and beachcomber TestDocs* regions run on their Postgres harnesses
- concept map rows link their guide pages and the not-provided rows the
  Frontend and AJAX page; index lists Backend, Database and Services
- TestDocsRequiredPages asserts the D-08 section order

modules/beachcomber/typesense/example_test.go

@@ -0,0 +1,49 @@
+package typesense_test
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strconv"
+	"time"
+
+	"git.golem15.com/golem15/summercms/modules/beachcomber"
+	"git.golem15.com/golem15/summercms/modules/beachcomber/typesense"
+)
+
+func ExampleEngine_SearchIDs() {
+	// A stand-in Typesense node.
+	node := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		q := r.URL.Query()
+		fmt.Println(r.Method, r.URL.Path, "key sent:", r.Header.Get("X-TYPESENSE-API-KEY") != "")
+		fmt.Println("q", q.Get("q"), "query_by", q.Get("query_by"), "filter_by", q.Get("filter_by"))
+		fmt.Fprint(w, `{"hits":[{"document":{"id":"3"}},{"document":{"id":"1"}}]}`)
+	}))
+	defer node.Close()
+	u, _ := url.Parse(node.URL)
+	port, _ := strconv.Atoi(u.Port())
+
+	engine := typesense.New(typesense.Config{
+		APIKey:            "test-only-key", // SUMMER_SEARCH__TYPESENSE__API_KEY
+		Host:              u.Hostname(),
+		Port:              port,
+		Protocol:          "http",
+		ConnectionTimeout: 2 * time.Second,
+	})
+	ids, err := engine.SearchIDs(context.Background(), "acme_blog_posts", beachcomber.Query{
+		Q:        "go",
+		QueryBy:  []string{"title"},
+		FilterBy: "blog_id:=7",
+	})
+	fmt.Println(ids, err)
+
+	// Without an API key the engine is not configured and nothing is sent.
+	fmt.Println(typesense.New(typesense.Config{}).Configured())
+	// Output:
+	// GET /collections/acme_blog_posts/documents/search key sent: true
+	// q go query_by title filter_by blog_id:=7
+	// [3 1] <nil>
+	// false
+}