[LD-163] Add access token encryption.

[nowakweronika]

Pull-Request

Description

Why?

We want to have access token encrypted to make it safer. I added a new task and PR because the last one was marked as done and it was easier for me to create a new branch.

What?

Added access token encryption with androidx security.

Links to related issues

• Fixes LD-163
• Based on: [LD-24] Add access token encryption. #118
• Previous task: https://loudius.atlassian.net/browse/LD-24

Demo

Nothing to show :)

How to test

• Step 1: Describe step 1
• Step 2: Describe step 2
• Expected: Describe what is expected to happen

Documentation

• Link to documentation: https://developer.android.com/jetpack/androidx/releases/security

Checklist

• Functionality is covered by unit tests
• Functionality is covered by integration tests
• I've updated PR description with relevant information
• I've done self code review
• I've manually tested if the code and app works