Returns the first non-empty refresh token among the candidates.
Providers may omit refresh_token or return ""; callers must not treat
empty strings as a new grant that should overwrite a stored token.
Parameters
...candidates: string[]
Candidate refresh token values in priority order.
Returns string
The first trimmed non-empty value, or '' when none are usable.
Returns the first non-empty refresh token among the candidates. Providers may omit
refresh_tokenor return""; callers must not treat empty strings as a new grant that should overwrite a stored token.