[M8] cargoxx-pkgs as a flake: cargoxx add → string-form dep

Wrapper: fix cache.nixos.org-1 key; drop AppImage; pin publish to mozart/cargoxx-pkgs.

tests/manifest_parse.cpp

@@ -181,16 +181,21 @@ optimize = "max"
     REQUIRE(r.error().code == ErrorCode::ManifestUnknownField);
 }
 
-TEST_CASE("parse accepts reserved [package] fields", "[manifest][parse]") {
+TEST_CASE("parse stores description / repository / homepage on Package",
+          "[manifest][parse]") {
     auto p = write_manifest(R"(
 [package]
 name = "foo"
 version = "0.1.0"
 description = "demo"
 repository = "https://example.com/foo"
+homepage = "https://example.com"
 )");
     auto r = parse(p);
     REQUIRE(r.has_value());
+    REQUIRE(r->package.description == "demo");
+    REQUIRE(r->package.repository == "https://example.com/foo");
+    REQUIRE(r->package.homepage == "https://example.com");
 }
 
 TEST_CASE("parse accepts reserved top-level tables", "[manifest][parse]") {