Refactor unix domain socket store config (#11109)

Following what is outlined in #10766 refactor the uds-remote-store such
that the member variables (state) don't live in the store itself but in
the config object.

Additionally, the config object includes a new necessary constructor
that takes a scheme & authority.

Tests are commented out because of linking errors with the current config system.
When there is a new config system we can reenable them.

Co-authored-by: John Ericson <John.Ericson@Obsidian.Systems>

src/libstore/ssh-store.hh

@@ -3,6 +3,7 @@
 
 #include "common-ssh-store-config.hh"
 #include "store-api.hh"
+#include "local-fs-store.hh"
 #include "remote-store.hh"
 
 namespace nix {
@@ -25,4 +26,26 @@ struct SSHStoreConfig : virtual RemoteStoreConfig, virtual CommonSSHStoreConfig
     std::string doc() override;
 };
 
+struct MountedSSHStoreConfig : virtual SSHStoreConfig, virtual LocalFSStoreConfig
+{
+    using LocalFSStoreConfig::LocalFSStoreConfig;
+    using SSHStoreConfig::SSHStoreConfig;
+
+    MountedSSHStoreConfig(StringMap params);
+
+    MountedSSHStoreConfig(std::string_view scheme, std::string_view host, StringMap params);
+
+    const std::string name() override
+    {
+        return "Experimental SSH Store with filesystem mounted";
+    }
+
+    std::string doc() override;
+
+    std::optional<ExperimentalFeature> experimentalFeature() const override
+    {
+        return ExperimentalFeature::MountedSSHStore;
+    }
+};
+
 }