test: unit tests for the admin class functions, the models and the admin registration

- classes: every admin action for its changed-row count and idempotency, the ban across several throttle rows, the cleanup of a permanent delete
- classes: the privileged list and IsPrivilegedMember (D-30), also through a handle that carries conditions
- classes: the five-minute boundary of last_seen
- models: PermissionSet round trip, the slug table shared with the SPA, Fillable and Rules, fields that never marshal, the group filter value
- TestAdminRegistration: permissions, navigation, embedded files and phrase keys in en and pl; the admin secret is required

models/slug_test.go

@@ -0,0 +1,53 @@
+package models
+
+import (
+	"strings"
+	"testing"
+)
+
+// slugCases is the table the admin SPA's slug preset is tested against as
+// well (admin/tests/form/formState.test.ts in the framework repository,
+// "slug preset matches the server rule"): the organisation model and the form
+// must derive the same slug from the same name.
+var slugCases = []struct{ text, want string }{
+	{"Acme Records", "acme-records"},
+	{"  Acme -- Records ", "acme-records"},
+	{"ACME_Records 2", "acme-records-2"},
+	{"Zażółć gęślą", "za-g-l"},
+	{"Rock & Roll!!!", "rock-roll"},
+	{"...leading and trailing...", "leading-and-trailing"},
+	{"tab\tand\nnewline", "tab-and-newline"},
+	{"emoji 🎵 music", "emoji-music"},
+	{"CamelCaseText", "camelcasetext"},
+	{"9 lives", "9-lives"},
+	{"a", "a"},
+	{"---", ""},
+	{"   ", ""},
+	{"", ""},
+	{"ąęść", ""},
+	{strings.Repeat("Long Name ", 40), strings.TrimSuffix(strings.Repeat("long-name-", 40), "-")},
+}
+
+func TestSlugifyTable(t *testing.T) {
+	for _, tc := range slugCases {
+		if got := Slugify(tc.text); got != tc.want {
+			t.Errorf("Slugify(%q) = %q, want %q", tc.text, got, tc.want)
+		}
+	}
+	// A slug is a fixed point, and it only holds lower-case ASCII letters,
+	// digits and single hyphens between them.
+	for _, tc := range slugCases {
+		slug := Slugify(tc.text)
+		if again := Slugify(slug); again != slug {
+			t.Errorf("Slugify(Slugify(%q)) = %q, want %q", tc.text, again, slug)
+		}
+		if strings.HasPrefix(slug, "-") || strings.HasSuffix(slug, "-") || strings.Contains(slug, "--") {
+			t.Errorf("Slugify(%q) = %q has a stray hyphen", tc.text, slug)
+		}
+		for _, r := range slug {
+			if !(r >= 'a' && r <= 'z') && !(r >= '0' && r <= '9') && r != '-' {
+				t.Errorf("Slugify(%q) = %q holds %q", tc.text, slug, r)
+			}
+		}
+	}
+}