OAuth authorize endpoint (Authorization Code + PKCE)

Initiates the Authorization Code + PKCE flow: 1. Validates client_id exists and is enabled 2. Validates redirect_uri is in whitelist (exact match only) 3. Validates PKCE code_challenge_method (must be S256 if provided) 4. Stores state token with PKCE parameters in Redis (5 minutes TTL) 5. Redirects to login page with OAuth parameters # Arguments * `realm_id` - Realm identifier * `params` - OAuth query parameters (client_id, redirect_uri, state, response_type, code_challenge, code_challenge_method) # Returns * 302 redirect to login page with OAuth parameters # Errors * 400 - Invalid parameters (missing client_id, redirect_uri, state, or code_challenge) * 400 - Invalid response_type (must be "code") * 400 - Unsupported code_challenge_method (must be "S256") * 404 - Client not found or disabled * 400 - Redirect URI not in whitelist

curl -X GET "https://example.com/api/oauth/string/authorize?client_id=string&redirect_uri=string&state=string&response_type=string&code_challenge=string"

{  "code": "string",  "details": null,  "message": "string",  "requestId": "string",  "status": 0}

{  "code": "string",  "details": null,  "message": "string",  "requestId": "string",  "status": 0}