libstore: Implement getHumanReadableURI for S3BinaryCacheStoreConfig

This slightly improves the logs situation by including the region/profile/endpoint
in the logs when S3 store references get printed. Instead of:

copying path '/nix/store/lxnp9cs4cfh2g9r2bs4z7gwwz9kdj2r9-test-package-c' to 's3://bucketname'...

This now includes:

copying path '/nix/store/lxnp9cs4cfh2g9r2bs4z7gwwz9kdj2r9-test-package-c' to 's3://bucketname?endpoint=http://server:9000&region=eu-west-1'...

Author: xokdvium

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

@@ -75,6 +75,8 @@ struct S3BinaryCacheStoreConfig : HttpBinaryCacheStoreConfig
     static StringSet uriSchemes();
 
     static std::string doc();
+
+    std::string getHumanReadableURI() const override;
 };
 
 } // namespace nix

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

@@ -29,6 +29,19 @@ S3BinaryCacheStoreConfig::S3BinaryCacheStoreConfig(
     }
 }
 
+std::string S3BinaryCacheStoreConfig::getHumanReadableURI() const
+{
+    auto reference = getReference();
+    reference.params = [&]() {
+        Params relevantParams;
+        for (auto & setting : s3UriSettings)
+            if (setting->overridden)
+                relevantParams.insert({setting->name, reference.params.at(setting->name)});
+        return relevantParams;
+    }();
+    return reference.render();
+}
+
 std::string S3BinaryCacheStoreConfig::doc()
 {
     return R"(