Add idempotency (#6748)

* added idempotency router and middleware

* added idempotency rules for routes classes, functions, jobs, installaions, users

* fixed typo

* ignore requests without header

* removed unused var

* enabled feature only for MongoDB

* changed code comment

* fixed inconsistend storage adapter specification

* Trigger notification

* Travis CI trigger

* Travis CI trigger

* Travis CI trigger

* rebuilt option definitions

* fixed incorrect import path

* added new request ID header to allowed headers

* fixed typescript typos

* add new system class to spec helper

* fixed typescript typos

* re-added postgres conn parameter

* removed postgres conn parameter

* fixed incorrect schema for index creation

* temporarily disabling index creation to fix postgres issue

* temporarily disabling index creation to fix postgres issue

* temporarily disabling index creation to fix postgres issue

* temporarily disabling index creation to fix postgres issue

* temporarily disabling index creation to fix postgres issue

* temporarily disabling index creation to fix postgres issue

* temporarily disabling index creation to fix postgres issue

* trying to fix postgres issue

* fixed incorrect auth when writing to _Idempotency

* trying to fix postgres issue

* Travis CI trigger

* added test cases

* removed number grouping

* fixed test description

* trying to fix postgres issue

* added Github readme docs

* added change log

* refactored tests; fixed some typos

* fixed test case

* fixed default TTL value

* Travis CI Trigger

* Travis CI Trigger

* Travis CI Trigger

* added test case to increase coverage

* Trigger Travis CI

* changed configuration syntax to use regex; added test cases

* removed unused vars

* removed IdempotencyRouter

* Trigger Travis CI

* updated docs

* updated docs

* updated docs

* updated docs

* update docs

* Trigger Travis CI

* fixed coverage

* removed code comments

src/Adapters/Storage/Postgres/PostgresStorageAdapter.js

@@ -1209,6 +1209,7 @@ export class PostgresStorageAdapter implements StorageAdapter {
             '_GlobalConfig',
             '_GraphQLConfig',
             '_Audience',
+            '_Idempotency',
             ...results.map((result) => result.className),
             ...joins,
           ];
@@ -2576,9 +2577,9 @@ export class PostgresStorageAdapter implements StorageAdapter {
     fieldNames: string[],
     indexName: ?string,
     caseInsensitive: boolean = false,
-    conn: ?any = null
+    options?: Object = {},
   ): Promise<any> {
-    conn = conn != null ? conn : this._client;
+    const conn = options.conn !== undefined ? options.conn : this._client;
     const defaultIndexName = `parse_default_${fieldNames.sort().join('_')}`;
     const indexNameOptions: Object =
       indexName != null ? { name: indexName } : { name: defaultIndexName };