Unified Storage: Add SQL template package (#87524)

* added sqltemplate package

* addded example

* fix linting issues

* improve code readability

* fix documentation

pkg/services/store/entity/sqlstash/sqltemplate/args_test.go

@@ -0,0 +1,34 @@
+package sqltemplate
+
+import (
+	"testing"
+)
+
+func TestArgs_Arg(t *testing.T) {
+	t.Parallel()
+
+	shouldBeQuestionMark := func(t *testing.T, s string) {
+		t.Helper()
+		if s != "?" {
+			t.Fatalf("expecting question mark, got %q", s)
+		}
+	}
+
+	a := new(Args)
+
+	shouldBeQuestionMark(t, a.Arg(0))
+	shouldBeQuestionMark(t, a.Arg(1))
+	shouldBeQuestionMark(t, a.Arg(2))
+	shouldBeQuestionMark(t, a.Arg(3))
+	shouldBeQuestionMark(t, a.Arg(4))
+
+	for i, arg := range *a {
+		v, ok := arg.(int)
+		if !ok {
+			t.Fatalf("unexpected value: %T(%v)", arg, arg)
+		}
+		if v != i {
+			t.Fatalf("unexpected int value: %v", v)
+		}
+	}
+}