Show manager request notifications for low-score users

[raymondjacobson]

Summary

• allow private manager request notification types to bypass the aggregate-user score cutoff while still requiring the referenced user to be current and active
• add a regression test for request_manager notifications from low-score grantor accounts

Prod evidence

• pending grant exists for @ray62926 -> @Rayjacobson at block 120202429
• raw notification row exists for user id 1 with type request_manager
• /v1/notifications/7eP5n?types=request_manager currently returns empty because @ray62926 has aggregate_user.score = -111

Tests

• go test ./api -run TestV1Notifications
• go test ./api