Cannot use filter relative interval on breakout fields (#28799) (#28930)

Fixes #25378

When using a relative filter with a starting from n units ago on an
aggregation with the same units, we were incorrectly assuming that we
would be working with a field ref at the top level. However, in this
scenario the field is nested such as `[:+ [:field $created_at
{:temporal-unit :month}] [:interval 1 :month]]`. This change makes sure
that we are altering the field-ref.

Co-authored-by: Case Nelson <case@metabase.com>

e2e/test/scenarios/filters/reproductions/25378-relative-date-on-breakout.cy.spec.js

@@ -24,7 +24,7 @@ const questionDetails = {
   display: "line",
 };
 
-describe.skip("issue 25378", () => {
+describe("issue 25378", () => {
   beforeEach(() => {
     restore();
     cy.signInAsAdmin();

src/metabase/query_processor/middleware/optimize_temporal_filters.clj

@@ -69,7 +69,9 @@
   (:end (u.date/range t unit)))
 
 (defn- change-temporal-unit-to-default [field]
-  (mbql.u/update-field-options field assoc :temporal-unit :default))
+  (mbql.u/replace field
+    [:field _ (_ :guard (comp optimizable-units :temporal-unit))]
+    (mbql.u/update-field-options &match assoc :temporal-unit :default)))
 
 (defmulti ^:private temporal-value-lower-bound
   "Get a clause representing the *lower* bound that should be used when converting a `temporal-value-clause` (e.g.

test/metabase/query_processor/middleware/optimize_temporal_filters_test.clj

@@ -353,3 +353,27 @@
                 {:source-query
                  {:source-table $$checkins
                   :filter       [:= [:field %date {:temporal-unit :month}] [:relative-datetime -1 :month]]}})))))))
+
+(deftest optimize-filter-with-nested-compatible-field
+  (testing "Should optimize fields when starting n :temporal-unit ago (#25378)"
+    (mt/$ids users
+      (is (= (mt/mbql-query users
+                            {:filter [:and
+                                      [:>=
+                                       [:+ [:field %last_login {:temporal-unit :default}] [:interval 3 :month]]
+                                       [:relative-datetime -12 :month]]
+                                      [:<
+                                       [:+ [:field %last_login {:temporal-unit :default}] [:interval 3 :month]]
+                                       [:relative-datetime 1 :month]]]
+                             :source-query {:source-table $$users
+                                            :aggregation [[:count]]
+                                            :breakout [[:field %last_login {:temporal-unit :month}]]}})
+             (optimize-temporal-filters/optimize-temporal-filters
+               (mt/mbql-query users
+                              {:filter [:between
+                                        [:+ [:field %last_login {:temporal-unit :month}] [:interval 3 :month]]
+                                        [:relative-datetime -12 :month]
+                                        [:relative-datetime 0 :month]]
+                               :source-query {:source-table $$users
+                                              :aggregation [[:count]]
+                                              :breakout [[:field %last_login {:temporal-unit :month}]]}})))))))