[SDK-3186] Support date/time custom claim validation

[jimmyjames]

Changes

Adds a new verification method to verify a custom date/time claim: Verification#withClaim(String name, Instant value)

Notes:

• Default implementation delegates to existing withClaim(String name, Date value) method to avoid breaking changes
• The current Date-based claim validation delegates to the new Instant-based validation, allowing us to remove Date-based validation code
• The current custom Date-based claim verification was arguably broken, or at least not intuitive. Because date claims are serialized as seconds since the epoch, any expected Date claim would need to have its milliseconds set to zero to be considered equal. This change fixes that by truncating the expected claim's value to seconds.

References

Builds on #537

[jimmyjames]

Changing the date time to include milliseconds causes this test to fail without the change to truncate milliseconds, demonstrating the issue with current custom Date-based claim validation

[jimmyjames]

Codecov failing because default implementation isn't covered. I'll look into adding a test for that (and other default implementations in that interface).

[jimmyjames]

Codecov failing because default implementation isn't covered. I'll look into adding a test for that (and other default implementations in that interface).

Additional tests added for default method implementations in Verification instance, as well as for the null handling of Verification implementation methods.

[poovamraj]

Hey Jim, left a couple of subjective points on the PR. let me know what you think of it