fix ajv config

Author: Sylvestre Gug

lib/validate.js

@@ -1,6 +1,6 @@
 import Ajv from "ajv";
 
-const ajv = new Ajv();
+const ajv = new Ajv({allowUnionTypes: true});
 
 export const validateQueryPayload = ajv.compile({
   type: "object",
@@ -18,6 +18,6 @@ export const validateDescribeColumnsPayload = ajv.compile({
   properties: {
     catalog: {type: "string", minLength: 1, maxLength: 32 * 1000},
     schema: {type: "string", minLength: 1, maxLength: 32 * 1000},
-    table: {type: "string", minLength: 1, maxLength: 32 * 1000}
+    table: {type: "string", minLength: 1, maxLength: 32 * 1000},
   },
-})
+});