[Feature Request] Token return from AcquireTokenByCredential doesn't contain RefreshToken

[zhetanuber]

Is your feature request related to a problem? Please describe.
I am trying to use the AcquireTokenSilent for my service to service credential client auth call, but get error with "no token found"
The underlying issue is that no RefreshToken found.

I check the token response of AcquireTokenByCredential, it doesn't contain RefreshToken either
Not sure if I miss anything or this library doesn't support AcquireTokenSilent for service to service auth

Describe the solution you'd like
I follow this code client_secret_sample.go
But it doesn't work for my service to service call case.
Currently I don't have any cache solution unless I implement a cache on my service side, is there any other cache option for my case?

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[bgavrilMS]

There is no refresh token in the client_credentials flow. Entra token issuer does not emit one. There is no need for one, because you can just use the secret / cert to get a fresh token.

AcquireTokenByCredential will pull tokens out of the cache on its own. You do not need to use AcquireTokenSilent. You do not need to serialize the cache, just keep a hold of the Confidential.Client object.

I have a PR out to update the sample:

#466