Add query param to filter users by 'external' & 'blocked' type on API

What does this MR do?

It adds query parameters to filter users based on external and blocked state.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

This is proposed feature. This way API clients don't have to filter the users based on blocked and external

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #23731 (closed)