Add Memory Database implementation instructions

These instructions are meant to give additional information for
alternative implementation which doesn't use MongoDB.

Signed-off-by: Georgi Michev <georgi.michev@vereign.com>

README.md

@@ -28,14 +28,21 @@ This repository holds the test automation framework based on Java and used for t
 _{BASE_URL} - should be replaced with the path where the services are deployed:  
 example: http://localhost_
 
-### Database
-In order for the test scenarios to be properly executed a MongoDB database deployment is needed.
+## Specifications for different database implementations
+### MongoDB
 The database should have specific structure and imported actual data.
 The structure and the data should follow the examples in **test_data** folder.
 Part of the data is also available in the Policies repository.  
 _-The ID fields can be ignored, they are usually created automatically by the database._  
 _-The JSON extensions of the files are just for formatting purposes._
 
+### Memory Storage
+If the depoloyment [instructions](https://gitlab.eclipse.org/eclipse/xfsc/tsa/policy/-/blob/main/doc/memory-storage.md)
+are followed correctly and the linked repository in `POLICY_REPOSITORY_CLONE_URL`
+environment variable contains all policies from **test_data** folder, all **policy** tests should pass.
+There will be failing tests in the other services due to the missing data needed for
+infohub and tasks services.
+
 # Manual execution
 To simplify manual tests execution we have a postman collection with the list of supported endpoints, you can find [here](postman/TSA.postman_collection.json)