[Backend] Implemented role request feature

[amlannandy]

Description

This PR creates a Blueprint for handling role change requests. It has 4 routes and implements the following features -

1. A user with an extractor or management role can submit a request to change their role to something else.
2. An admin can view all the role change requests submitted by its created users.
3. The admin can either approve or reject these role change requests.

Fixes #127

Type of change

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Shown in Demo Video

Test Configuration:

• Postman
• Windows 10

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules