[2.7] adds deprecation notices.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | yes
| Tests pass?   | yes
| Fixed tickets | ~
| License       | MIT
| Doc PR        | ~

this is registered by the subscriber, so it should not trigger the deprecation all the time. You should trigger it only when you don't have the RequestStack (and actually, a better way to handle it would be to trigger a deprecation in the constructor when the RequestStack is not provided)