@Nullable open fun readAccessTokenCompat(clientSecret: String!): TokenResponse?
Reads the stored access token, if a valid one is stored.
clientSecret - String!: The client secret, used for the purpose of decrypting the token as it was encrypted by the old one. If null, a check for old sdk credentials is skipped, otherwise it is performed
Return
TokenResponse?: The stored access token, if any. null otherwise.