[Minor] Rbl: Allow to add dependencies for RBL rules

lualib/plugins/rbl.lua

@@ -113,6 +113,9 @@ local rule_schema_tbl = {
   received = ts.boolean:is_optional(),
   replyto = ts.boolean:is_optional(),
   requests_limit = (ts.integer + ts.string / tonumber):is_optional(),
+  require_symbols = (
+      ts.array_of(ts.string) + (ts.string / function(s) return {s} end)
+  ):is_optional(),
   resolve_ip = ts.boolean:is_optional(),
   return_bits = return_bits_schema:is_optional(),
   return_codes = return_codes_schema:is_optional(),

src/plugins/lua/rbl.lua

@@ -1025,6 +1025,12 @@ local function add_rbl(key, rbl, global_opts)
       rspamd_config:register_dependency(rbl.symbol, 'DKIM_CHECK')
     end
 
+    if rbl.require_symbols then
+      for _,dep in ipairs(rbl.require_symbols) do
+        rspamd_config:register_dependency(rbl.symbol, dep)
+      end
+    end
+
     -- Failure symbol
     rspamd_config:register_symbol{
       type = 'virtual',