Add settings page to delete user

[FelixTJDietrich]

Motivation

We need to let users delete their account to be compliment with GDPR.

Description

• Add setting page
• Add setting button to user menu
• Add endpoint to delete user (currently just the keycloak user)
• Fix void response for OpenAPI
• Update default keycloak config data with a correctly setup admin client

Testing Instructions

Create an account and delete it via the settings.

Screenshots (if applicable)

Checklist

General

• [x] PR title is clear and descriptive
• [x] PR description explains the purpose and changes
• [x] Code follows project coding standards
• [x] Self-review of the code has been done
• [x] Changes have been tested locally
• [x] Screenshots have been attached (if applicable)
• [ ] Documentation has been updated (if applicable)

Client (if applicable)

• [x] UI changes look good on all screen sizes and browsers
• [x] No console errors or warnings
• [ ] User experience and accessibility have been tested
• [ ] Added Storybook stories for new components
• [ ] Components follow design system guidelines (if applicable)

Server (if applicable)

• [x] Code is performant and follows best practices
• [ ] No security vulnerabilities introduced
• [ ] Proper error handling has been implemented
• [ ] Added tests for new functionality
• [ ] Changes have been tested in different environments (if applicable)