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/Controllers/types.js

@@ -0,0 +1,29 @@
+export type LoadSchemaOptions = {
+  clearCache: boolean
+};
+
+export type SchemaField = {
+  type: string;
+  targetClass?: ?string;
+}
+
+export type SchemaFields = { [string]: SchemaField }
+
+export type Schema = {
+  className: string,
+  fields: SchemaFields,
+  classLevelPermissions: ClassLevelPermissions,
+  indexes?: ?any
+};
+
+export type ClassLevelPermissions = {
+  find?: {[string]: boolean};
+  count?: {[string]: boolean};
+  get?: {[string]: boolean};
+  create?: {[string]: boolean};
+  update?: {[string]: boolean};
+  delete?: {[string]: boolean};
+  addField?: {[string]: boolean};
+  readUserFields?: string[];
+  writeUserFields?: string[];
+};