Create Member Registration Endpoint

Implement a POST /api/v1/members/register endpoint to allow new members to join a chama group.
Requirements:

Accepts JSON payload:

{
"full_name": "string",
"email": "string",
"phone": "string",
"password": "string"
}

Validate:

Email must be unique

Password ≥ 8 chars

Phone must be valid format (+2547...)

Hash passwords using bcrypt

Return success message and JWT token on success

Status codes:

201 Created — registration success

400 — invalid data

409 — email or phone already exists