explicit run time limits for the datalog engine

[Geal]

right now, we put some hardcoded limits on the number of iterations in a "world run", but it should be better to leave that decision to the user. We can get a token with some degenerate cases that would produce a lot of facts or apply on a large number of iterations, so there should be a hard limit there.

A few options:

• limit on the number of facts produced
• limit on the execution time
• if we want a safer way, optionally forbid facts and rules in blocks other than authority (so those blocks would only contain caveats)

[Geal]

implemented in the Rust version: biscuit-auth/biscuit-rust@afa0042
@daeMOn63 @titanous do you have such options for the Go version?

[Geal]

Java version: CleverCloud/biscuit-java@ff9c2f6

[daeMOn63]

Implemented in Go version: biscuit-auth/biscuit-go@1f63389