//Add the Refresh token
public async Task <bool> AddRefreshToken(RefreshToken token)
{
var existingToken = context.RefreshTokens.FirstOrDefault(r => r.UserName == token.UserName &&
r.ClientID == token.ClientID);
if (existingToken != null)
{
var result = await RemoveRefreshToken(existingToken);
}
context.RefreshTokens.Add(token);
return(await context.SaveChangesAsync() > 0);
}