Introduces flow types for storage (#4349)

* Introduces flow types for storage

* Better typing of QueryOptions

* Adds flow types to SchemaCOntroller,

- runs flow on pre tests
- fixes flow

* Adds ClassLevelPermissions type

* Moves Controller types into a single file

* Changes import styles

* Changes import styles

* fixing method setIndexesWithSchemaFormat (#4454)

Fixing invalid database code in method `setIndexesWithSchemaFormat`:

* It must be a transaction, not a task, as it executes multiple database changes
* It should contain the initial queries inside the transaction, providing the context, not outside it;
* Replaced the code with the ES6 Generator notation
* Removing the use of batch, as the value of the result promise is irrelevant, only success/failure that matters

* nits

* Fixes tests, improves flow typing

src/Adapters/Storage/Mongo/MongoSchemaCollection.js

@@ -137,6 +137,18 @@ class MongoSchemaCollection {
     return this._collection._mongoCollection.findAndRemove(_mongoSchemaQueryFromNameQuery(name), []);
   }
 
+  insertSchema(schema: any) {
+    return this._collection.insertOne(schema)
+      .then(result => mongoSchemaToParseSchema(result.ops[0]))
+      .catch(error => {
+        if (error.code === 11000) { //Mongo's duplicate key error
+          throw new Parse.Error(Parse.Error.DUPLICATE_VALUE, 'Class already exists.');
+        } else {
+          throw error;
+        }
+      })
+  }
+
   updateSchema(name: string, update) {
     return this._collection.updateOne(_mongoSchemaQueryFromNameQuery(name), update);
   }