fix: accept invite functionality should use transactions for atomicity

[ztmbuilds]

Description

This PR addresses an issue in accepting invites. It wraps all database operations in a transaction making them atomic. Previously, multiple resources (invite, user, organisationUserRole) were being updated outside a transaction, which could lead to potential data inconsistencies

Related Issue

Fixes #1259

Type of Change

• feat: New feature
• fix: Bug fix
• docs: Documentation updates
• style: Code style/formatting changes
• refactor: Code refactoring
• perf: Performance improvements
• test: Test additions/updates
• chore: Build process or tooling changes
• ci: CI configuration changes
• other:

How Has This Been Tested?

• Unit tests
• Integration tests
• Manual tests

Test Evidence

Checklist

• My code follows the project's coding style
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published
• I have included a screenshot showing all tests passing
• I have included documentation screenshots (if applicable)