Expose OAuth token management parameters across all providers

[jlowin]

Closes #2208

All OAuth providers and the OIDC proxy now expose the three production-critical parameters for persistent token management across server restarts:

• jwt_signing_key: Secret for signing FastMCP JWT tokens
• token_encryption_key: Secret for encrypting upstream OAuth tokens at rest
• client_storage: AsyncKeyValue storage for persisting client registrations

What Changed

OIDCProxy now accepts and passes through both encryption parameters to OAuthProxy.

All provider classes now expose all three parameters:

• GoogleProvider
• GitHubProvider
• AzureProvider
• WorkOSProvider
• Auth0Provider
• AWSCognitoProvider

Production Usage

import os
from fastmcp import FastMCP
from fastmcp.server.auth.providers.google import GoogleProvider
from key_value.aio.stores.redis import RedisStore

auth = GoogleProvider(
    client_id="...",
    client_secret="...",
    base_url="https://production.com",
    
    # Production token management
    jwt_signing_key=os.environ["JWT_SIGNING_KEY"],
    token_encryption_key=os.environ["TOKEN_ENCRYPTION_KEY"],
    client_storage=RedisStore(
        host=os.environ["REDIS_HOST"],
        port=int(os.environ["REDIS_PORT"])
    )
)

mcp = FastMCP("Production App", auth=auth)

All three parameters work together to ensure tokens and registrations survive restarts in distributed deployments.

Documentation

Added "Production Configuration" sections (with version badges) to all provider integration guides demonstrating complete setup with Redis and environment variables.