feat(mcp): add --database-url CLI option for direct Redis connections

[joshrotenberg]

Summary

Add support for connecting to Redis databases via URL without requiring a profile. This is useful for ad-hoc connections to standalone Redis instances that aren't configured as profiles.

Changes

• Add --database-url option to mcp serve command (also supports REDIS_URL env var)
• Add DatabaseTools::new_from_url() constructor for URL-based connections
• Update get_database_tools() to prefer URL over profile when both available
• Update MCP documentation with both connection approaches (URL and profile-based)
• Add unit test for database_url configuration

Usage

# Via command line
redisctl mcp serve --database-url redis://localhost:6379

# Via environment variable
REDIS_URL=redis://localhost:6379 redisctl mcp serve

# With authentication
redisctl mcp serve --database-url redis://:password@localhost:6379

# TLS connection
redisctl mcp serve --database-url rediss://default:password@host:6379

The URL format follows the standard Redis URL scheme:
redis[s]://[[username:]password@]host[:port][/db]

Why

Users may want to use the MCP server with a Redis database that isn't managed by Redis Enterprise or Cloud (e.g., a local Redis instance, self-hosted Redis, or third-party managed Redis). This allows quick connections without needing to set up a profile first.