AddAccessToken creates and stores a new access token in the database.

AddRefreshToken creates and stores a new refresh token in the database.

GetAllAccessTokensByUserID returns all access tokens for a given user.

RemoveAccessToken deletes an access token from the database.

RemoveRefreshTokenByToken deletes a refresh token from the database.

ValidateAccessToken checks if the given token exists and is not expired.

ValidateRefreshToken checks if the given token exists and is not expired.