feat: add schemas for time crate ^0.3

[fwfurtado]

This pull request adds support for the time crate version 0.3 (as the optional time03 feature) to Schemars, allowing types from time (such as Date, Time, PrimitiveDateTime, and OffsetDateTime) to implement JsonSchema. It also includes tests and documentation updates for this new feature.

Support for the time03 feature:

• Added time03 as an optional dependency in schemars/Cargo.toml, with and without the serde feature for normal and testing builds. [1] [2]
• Updated the documentation in README.md to mention the new time03 feature flag.

Implementation for time03 types:

• Added a new module time03.rs implementing JsonSchema for Date, Time, PrimitiveDateTime, and OffsetDateTime, mapping them to appropriate JSON Schema string formats.
• Registered the new module behind the time03 feature flag in mod.rs.

Testing:

• Added integration tests for the new time03 types in time.rs, including snapshot testing and roundtrip checks.
• Added a corresponding snapshot file for the expected JSON Schema output.
• Registered the new test module in the integration test harness.

[marcelotozzi]

👍

[clementwanjau]

Looks good.

[gpluscb]

There is an issue with this that needs consideration: the default serialization format of time's types is not rfc3339 (see time-rs/time#672). Without external solutions like the serde_with crate, only OffsetDateTime supports an rfc3339 format by using #[serde(with = time::serde::rfc3339)]. Therefore by default there would be a discrepancy between the generated schema and the serialized data.

For OffsetDateTime the required serde attribute could be documented, for other types such as Time, PrimitiveDateTime, and Date the correct approach is not so clear.

Also if a solution is found that includes Time, PrimitiveDateTime and Date, then UtcDateTime should be added as well.

[matthiasbeyer]

I am interested in this (or #257) and would like to see it implemented. What can I do to help move this forward?

[matthiasbeyer]

@GREsau what is needed to drive this to completion?