Add exports to proxy plugin config

Allows external plugins to define exports.

Signed-off-by: Derek McGowan <derek@mcg.dev>

services/server/server.go

@@ -491,11 +491,17 @@ func LoadPlugins(ctx context.Context, config *srvconfig.Config) ([]plugin.Regist
 			p = platforms.DefaultSpec()
 		}
 
+		exports := pp.Exports
+		if exports == nil {
+			exports = map[string]string{}
+		}
+		exports["address"] = address
+
 		registry.Register(&plugin.Registration{
 			Type: t,
 			ID:   name,
 			InitFn: func(ic *plugin.InitContext) (interface{}, error) {
-				ic.Meta.Exports["address"] = address
+				ic.Meta.Exports = exports
 				ic.Meta.Platforms = append(ic.Meta.Platforms, p)
 				conn, err := clients.getClient(address)
 				if err != nil {