Add flags.reward_id filter variable

[Felanbird]

option for filtering redemptions based on their id

only technically needs to work for flags.reward_id == "41b15a27-2090-49b5-ae27-c72c41ee14c4 but flags.reward_id contains "41b15a27" is ok if the user really wants

[Felanbird]

added as reward.id in #5275