Configuration: Audit and improve authentication setup UX

[joshrotenberg]

Overview

Part of Phase 3 roadmap - improve user experience for authentication configuration.

Context

Currently users need to configure authentication through:

• Environment variables (REDIS_CLOUD_API_KEY, REDIS_ENTERPRISE_URL, etc.)
• Profile configuration files
• Command-line flags

This can be confusing compared to the typical curl nightmare they're used to. We need to make this more user-friendly.

Tasks

• Audit current configuration flow for both Cloud and Enterprise
• Document all authentication methods and their precedence
• Identify pain points in current setup
• Create interactive setup wizard for first-time users
• Add validation and helpful error messages for auth issues
• Support common authentication patterns (OAuth, API tokens, certificates)
• Add 'redisctl auth test' command to verify credentials

Acceptance Criteria

• Users can easily set up authentication on first use
• Clear error messages guide users to fix auth issues
• Documentation clearly explains all auth methods
• Interactive setup available for new users

Related to #3 (Phase 3 Roadmap)