support meta info for client and proxy

conf/frpc_full.ini

@@ -64,6 +64,10 @@ tls_enable = true
 # heartbeat_interval = 30
 # heartbeat_timeout = 90
 
+# additional meta info for client
+meta_var1 = 123
+meta_var2 = 234
+
 # 'ssh' is the unique proxy name
 # if user in [common] section is not empty, it will be changed to {user}.{proxy} such as 'your_name.ssh'
 [ssh]
@@ -92,6 +96,9 @@ health_check_timeout_s = 3
 health_check_max_failed = 3
 # every 10 seconds will do a health check
 health_check_interval_s = 10
+# additional meta info for each proxy
+meta_var1 = 123
+meta_var2 = 234
 
 [ssh_random]
 type = tcp