Update box proto to use struct for metadata

internal/server/proto/ruby_vagrant/ruby-server.pb.go

@@ -1,7 +1,7 @@
 // Code generated by protoc-gen-go. DO NOT EDIT.
 // versions:
 // 	protoc-gen-go v1.26.0
-// 	protoc        v3.15.8
+// 	protoc        v3.19.4
 // source: proto/ruby_vagrant/ruby-server.proto
 
 package ruby_vagrant

internal/server/proto/vagrant_server/server.proto

@@ -287,10 +287,9 @@ message Box {
   // This is the directory on disk where this box exists.
   string directory = 4;
 
-  // TODO: is this <string, string>?
   // This is the metadata for the box. This is read from the "metadata.json"
   // file that all boxes require.
-  map<string, string> metadata = 5;
+  google.protobuf.Struct metadata = 5;
 
   // This is the URL to the version info and other metadata for this
   // box.

lib/vagrant/protobufs/proto/vagrant_server/server_pb.rb

@@ -49,7 +49,7 @@ Google::Protobuf::DescriptorPool.generated_pool.build do
       optional :provider, :string, 2
       optional :version, :string, 3
       optional :directory, :string, 4
-      map :metadata, :string, :string, 5
+      optional :metadata, :message, 5, "google.protobuf.Struct"
       optional :metadata_url, :string, 6
       optional :name, :string, 7
       optional :last_update, :message, 8, "google.protobuf.Timestamp"