util.sql: Add safety check to ensure our chosen connection charset is actually being used (MySQL)

util/sql.lua

@@ -286,6 +286,18 @@ function engine:set_encoding() -- to UTF-8
 		return ok, err;
 	end
 	
+	if driver == "MySQL" then
+		local ok, actual_charset = self:transaction(function ()
+			return self:select"SHOW SESSION VARIABLES LIKE 'character_set_client'";
+		end);
+		for row in actual_charset do
+			if row[2] ~= charset then
+				log("error", "MySQL %s is actually %q (expected %q)", row[1], row[2], charset);
+				return false, "Failed to set connection encoding";
+			end
+		end
+	end
+	
 	return true;
 end
 local engine_mt = { __index = engine };