cacheTokens
Configures whether to cache the result of loadTokens.
When true (default), the result of loadTokens is cached and reused for subsequent requests. When false, loadTokens is called on every request, allowing external token management systems (like Firebase Auth) to provide fresh tokens without redundant caching.
Set this to false when:
You manage token caching externally (e.g., Firebase Auth, or other authentication SDKs)
You need fine-grained control over token lifecycle
You want to avoid calling BearerAuthProvider.clearToken on logout