Fix number can't be shared

[Mugisha146]

PR Description

This PR fix issue of multiple users from registering with the same phone number [https://github.com//pull/93].

Description of tasks that were expected to be completed

Bug Fix : To prevent multiple users from registering with the same phone number ( ensures each phone number can only be associated with a single user account).
This include add a validation checker that check if Telephone number already exists or used in register process by someone else then block he/him to register if number exist and display toast to notify him/her.

How has this been tested?

1. Clone the repository.
2. Checkout to the 117-fx-numbers-can-not-shared
3. Run npm install, then npm run dev to verify the app is functioning correctly.
4. Test the Register first and register at the second time with different details but same phone number then see if it work as expected.

With deployed Link: None

Track PR (issue number & link) : #117

-Issue #93

Screenshots (If appropriate especially on the frontend)
N/A

[Ishimwe7]

Well done @Mugisha146 , it is now working