Key security with Schedule

[mikera]

Convex provides the facility for a "schedule" of operations to be executed a later time from any Account.

There is a potential security risk, given the ability to rotate keys, that the schedule could be used to attack someone who might mistakenly assume that the current (rotated) key is secure, when in fact the scheduled op was issued earlier by a different (insecure) key.

Probably need to either:

• include the key in the Schedule at the time of scheduling, and enforce that this is the same key when the schedules operation is executed
• add timestamps when keys are rotated, and ensure that the scheduled op was scheduled with the current key value
• cancel previously scheduled transactions when keys are rotated (maybe too expensive to scan full schedule unless we add more indexing?)

[mikera]

Probable solution: add a timestamp *schedule-start* which defines at what time scheduled operations can begin. This can be cleared to block all scheduled operations.