[Backend] Add password strength validation for create user routes

[amlannandy]

Is your feature request related to a problem? Please describe. Password strength validation should be added while creating users to enhance the security.

Describe the solution you'd like A clear and concise description of what you want to happen.

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

Additional context I'll soon submit a PR for it.

[b-thebest]

Can I work on this issue or it is resolved?

[amlannandy]

@b-thebest I've already submitted a PR for it. #126