Support per-section GAM ad unit paths via gam_unit_path templates

CHANGELOG.md

@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Added the default-true `[auction].rewrite_creatives` option. Setting it to `false` preserves mandatory creative sanitization across `POST /auction` and publisher SSAT/page-bids delivery while skipping first-party resource/click URL rewriting; it also skips creative TSJS injection on `POST /auction`.
+- `creative_opportunities.slot.gam_unit_path` is now a template supporting `{network_id}`, `{slot_id}`, and `{section}`, so a publisher whose ad unit varies by site section expresses it in one slot rule instead of one per (slot × section). `{section}` derives from the request path: `[creative_opportunities].section_segment` selects which path segment names the section (0-based, default `0`; set `1` for locale-prefixed URLs), and `section_root` supplies the value for paths with no such segment. `section_root` is required when a template uses `{section}`. Existing static and absent `gam_unit_path` configs are unchanged. Startup rejects a blank `gam_network_id` only when an absent/default path or `{network_id}` template consumes it. Trusted Server conservatively caps whole rendered dynamic paths at 100 UTF-8 bytes, informed by Google's 100-character per-ad-unit-code limit; an over-limit request-specific path omits that slot without failing the response. During typed/startup finalization, every placeholder-bearing template that omits `section_segment` materializes `section_segment = 0`, so an older binary rejects the blob loudly. Static and absent paths remain legacy-schema compatible only when both `section_root` and `section_segment` are omitted. Before rolling back below this feature, replace or remove dynamic paths, remove both keys, re-push and finalize the config, then roll back the binary.
 - Added Osano consent mirror integration docs and public enablement guidance.
 - Implemented basic authentication for configurable endpoint paths (#73)
 - Added integrations guide with example `testlight` integration

crates/trusted-server-core/src/config.rs

@@ -218,6 +218,46 @@ mod tests {
     use super::*;
     use crate::test_support::tests::crate_test_settings_str;
 
+    #[derive(Debug, Deserialize)]
+    #[serde(deny_unknown_fields)]
+    #[allow(dead_code)]
+    struct LegacyCreativeOpportunitiesConfig {
+        gam_network_id: String,
+        #[serde(default)]
+        auction_timeout_ms: Option<u32>,
+        #[serde(default)]
+        price_granularity: serde_json::Value,
+        #[serde(default)]
+        slot: Vec<serde_json::Value>,
+    }
+
+    fn serialized_creative_opportunities(gam_unit_path: Option<&str>) -> serde_json::Value {
+        let mut toml = crate_test_settings_str();
+        toml.push_str(
+            r#"
+
+[creative_opportunities]
+gam_network_id = "99999"
+
+[[creative_opportunities.slot]]
+id = "example-slot"
+page_patterns = ["/*"]
+formats = [{ width = 300, height = 250 }]
+"#,
+        );
+        if let Some(gam_unit_path) = gam_unit_path {
+            toml.push_str(&format!("gam_unit_path = {gam_unit_path:?}\n"));
+        }
+
+        let app_config: TrustedServerAppConfig =
+            toml::from_str(&toml).expect("should deserialize app config wrapper");
+        serde_json::to_value(app_config)
+            .expect("should serialize app config wrapper")
+            .get("creative_opportunities")
+            .cloned()
+            .expect("should contain creative opportunities")
+    }
+
     fn valid_settings() -> Settings {
         let mut settings =
             Settings::from_toml(&crate_test_settings_str()).expect("should parse test settings");
@@ -254,6 +294,37 @@ mod tests {
         );
     }
 
+    #[test]
+    fn dynamic_gam_unit_templates_are_rejected_by_legacy_schema() {
+        for gam_unit_path in ["/{network_id}/example", "/example/{slot_id}"] {
+            let creative_opportunities = serialized_creative_opportunities(Some(gam_unit_path));
+            let err =
+                serde_json::from_value::<LegacyCreativeOpportunitiesConfig>(creative_opportunities)
+                    .expect_err("should reject dynamic GAM unit template");
+
+            assert!(
+                err.to_string().contains("section_segment"),
+                "legacy error should name section_segment: {err}"
+            );
+        }
+    }
+
+    #[test]
+    fn static_gam_unit_template_is_accepted_by_legacy_schema() {
+        let creative_opportunities = serialized_creative_opportunities(Some("/99999/example/home"));
+
+        serde_json::from_value::<LegacyCreativeOpportunitiesConfig>(creative_opportunities)
+            .expect("should accept static GAM unit template");
+    }
+
+    #[test]
+    fn absent_gam_unit_template_is_accepted_by_legacy_schema() {
+        let creative_opportunities = serialized_creative_opportunities(None);
+
+        serde_json::from_value::<LegacyCreativeOpportunitiesConfig>(creative_opportunities)
+            .expect("should accept absent GAM unit template");
+    }
+
     #[test]
     fn deploy_validation_rejects_placeholders() {
         let settings = Settings::from_toml(