Verification: clan tag setting, GroupVerify 0.3.0 wording

Root sets GroupVerify's clan_tag (the scoreboard tag CS2-Tags gives verified players without a
rank) next to the Steam group. Validated like the plugin (12 UTF-16 units, no quotes, ; or \),
saved to gv_settings and sent as css_gv_clantag when the plugin is loaded. Only changed fields
are sent.

GroupVerify 0.3.0 checks players with the Steam Web API as they join, so the group list is now
"Confirmed group members" with first/last confirmed dates.

internal/web/verify_test.go

@@ -23,6 +23,26 @@ func TestIsClanID(t *testing.T) {
 	}
 }
 
+func TestValidClanTag(t *testing.T) {
+	for tag, want := range map[string]bool{
+		"":              true,
+		"zio":           true,
+		"zio.sh":        true,
+		"twelve chars":  true,
+		"thirteen char": false,
+		"say \"hi\"":    false,
+		"a;quit":        false,
+		"back\\slash":   false,
+		"tab\there":     false,
+		"🙂🙂🙂🙂🙂🙂":        true,  // 12 UTF-16 units
+		"🙂🙂🙂🙂🙂🙂🙂":       false, // 14
+	} {
+		if got := validClanTag(tag); got != want {
+			t.Errorf("validClanTag(%q) = %v, want %v", tag, got, want)
+		}
+	}
+}
+
 func TestVerifyShown(t *testing.T) {
 	on := store.VerifySettings{Enabled: true, GroupID: "103582791429521412"}
 	for _, c := range []struct {