This PR introduces a structure called `FormatConfig`, which provides
additional configuration options for `GenericFormat`, such as whether
leap seconds should be allowed during parsing. By default, this option
is set to `false`.
This PR also fixes certain flaws to make the implementation less
permissive by:
- Disallowing the final leap second, such as `2016-12-31T23:59:60Z`,
when `allowLeapSeconds = false`.
- Disallowing invalid leap seconds, such as `2017-06-30T23:59:60Z`, when
`allowLeapSeconds = false`.
- Disallowing leap-minute time zones, such as
`2016-12-31T00:00:00+2360`, and out-of-range time zones, such as
`2016-12-31T00:00:00+2490`.
These changes ensure that Lean aligns with TypeScript's behavior, as
outlined in this table:
https://github.com/cedar-policy/cedar-spec/pull/519#issuecomment-2613547897.
