libstore: Simplify check for S3-specific URI query parameters

Instead of hardcoding strings we should instead use the setting
objects to determine the query names that should be preserved.

src/libstore/include/nix/store/s3-binary-cache-store.hh

@@ -21,8 +21,6 @@ struct S3BinaryCacheStoreConfig : HttpBinaryCacheStoreConfig
           Nix uses the `default` profile.
         )"};
 
-public:
-
     const Setting<std::string> region{
         this,
         "us-east-1",
@@ -63,6 +61,12 @@ public:
           > addressing instead of virtual host based addressing.
         )"};
 
+    /**
+     * Set of settings that are part of the S3 URI itself.
+     * These are needed for region specification and other S3-specific settings.
+     */
+    const std::set<const AbstractSetting *> s3UriSettings = {&profile, &region, &scheme, &endpoint};
+
     static const std::string name()
     {
         return "S3 Binary Cache Store";

src/libstore/s3-binary-cache-store.cc

@@ -1,10 +1,10 @@
 #include "nix/store/s3-binary-cache-store.hh"
-
-#include <cassert>
-
 #include "nix/store/http-binary-cache-store.hh"
 #include "nix/store/store-registration.hh"
 
+#include <cassert>
+#include <ranges>
+
 namespace nix {
 
 StringSet S3BinaryCacheStoreConfig::uriSchemes()
@@ -17,14 +17,13 @@ S3BinaryCacheStoreConfig::S3BinaryCacheStoreConfig(
     : StoreConfig(params)
     , HttpBinaryCacheStoreConfig(scheme, _cacheUri, params)
 {
-    // For S3 stores, preserve S3-specific query parameters as part of the URL
-    // These are needed for region specification and other S3-specific settings
     assert(cacheUri.query.empty());
+    assert(cacheUri.scheme == "s3");
 
-    // Only copy S3-specific parameters to the URL query
-    static const std::set<std::string> s3Params = {"region", "endpoint", "profile", "scheme"};
     for (const auto & [key, value] : params) {
-        if (s3Params.contains(key)) {
+        auto s3Params =
+            std::views::transform(s3UriSettings, [](const AbstractSetting * setting) { return setting->name; });
+        if (std::ranges::contains(s3Params, key)) {
             cacheUri.query[key] = value;
         }
     }