Find friends by phone number

[rubenhorn]

⚠ Blocked until friend or follower feature is defined and planned

• endpoint maps list of (name, phone_number) to list of (name, userID)
• Authentication required
• Prevent scraping using Hashcash (see [Suggestion] Use Hashcash to prevent spam #58)
• API documentation is updated
• GSI for user profile (phone_number -> userID)
• Privacy: Opt-In/Opt-Out