Remove always true expressions in OpenDD planning (#1719)

<!-- The PR description should answer 2 important questions: -->

### What

All of the execution plan mismatches had this in common - they passed an
`{}` to a filter. In OpenDD this leaves empty `And []` around the place,
where we used to erase them.

### How

Wherever we were using `Some(ResolvedFilterExpression::mk_and(exprs))`
we do
`ResolvedFilterExpression::mk_and(exprs).remove_always_true_expression()`
like old pipeline.

V3_GIT_ORIGIN_REV_ID: 18cbf20c88ac8a94c6ec78f8153c094351d52e60

Author: danieljharvey

v3/changelog.md

@@ -8,6 +8,9 @@
 
 ### Changed
 
+- Empty filter expressions are consistent between old and OpenDD execution
+  pipelines
+
 ### Fixed
 
 ## [v2025.03.10]

v3/crates/engine/tests/execute/models/select_many/where/null_input/expected.json

@@ -20,6 +20,16 @@
           "author_id": 2,
           "first_name": "John"
         }
+      ],
+      "AuthorManyWhereEmpty": [
+        {
+          "author_id": 1,
+          "first_name": "Peter"
+        },
+        {
+          "author_id": 2,
+          "first_name": "John"
+        }
       ]
     }
   },
@@ -36,6 +46,12 @@
           "author_id": 2,
           "first_name": "John"
         }
+      ],
+      "AuthorManyWhereEmpty": [
+        {
+          "author_id": 2,
+          "first_name": "John"
+        }
       ]
     }
   }

v3/crates/engine/tests/execute/models/select_many/where/null_input/request.gql

@@ -7,4 +7,8 @@ query ($where_input: AuthorFilter) {
     author_id
     first_name
   }
+  AuthorManyWhereEmpty: AuthorMany(where: {}) {
+    author_id
+    first_name
+  }
 }

v3/crates/plan/src/query/field_selection.rs

@@ -492,9 +492,9 @@ fn from_model_relationship(
 
             // combine existing filter with new ones
             if !relationship_join_filter_expressions.is_empty() {
-                query_execution.query_node.predicate = Some(ResolvedFilterExpression::mk_and(
-                    relationship_join_filter_expressions.into(),
-                ));
+                query_execution.query_node.predicate =
+                    ResolvedFilterExpression::mk_and(relationship_join_filter_expressions.into())
+                        .remove_always_true_expression();
             }
 
             // add the new arguments
@@ -978,10 +978,10 @@ fn from_relationship_aggregate_selection(
 
                     // combine existing filter with new ones
                     if !relationship_join_filter_expressions.is_empty() {
-                        query_execution.query_node.predicate =
-                            Some(ResolvedFilterExpression::mk_and(
-                                relationship_join_filter_expressions.into(),
-                            ));
+                        query_execution.query_node.predicate = ResolvedFilterExpression::mk_and(
+                            relationship_join_filter_expressions.into(),
+                        )
+                        .remove_always_true_expression();
                     }
 
                     // add the new arguments

v3/crates/plan/src/query/model_target.rs

@@ -99,7 +99,8 @@ pub fn model_target_to_ndc_query(
             permission_filter,
             filter,
         ])),
-    };
+    }
+    .and_then(ResolvedFilterExpression::remove_always_true_expression);
 
     let order_by_elements = model_target
         .order_by