Feature/default derive

[larsk2009]

Fixes #12.

I updated the unit tests to use the defaults where possible (not possible for arrays, as you get empty arrays). Maybe you don't want this as you might want all options to be Some where default will make them None. If so, I can remove #30848bc from this PR.

I also noticed one bug after using the default types in the unit tests. The status notification timestamp was missing a skip_serializing_if for the option type. That is also fixed in this PR.

[codecov-commenter]

Codecov Report

Base: 84.14% // Head: 77.61% // Decreases project coverage by -6.53% :warning:

Coverage data is based on head (4594806) compared to base (4cd78f9). Patch coverage: 87.58% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #13 +/- ## ========================================== - Coverage 84.14% 77.61% -6.54% ========================================== Files 281 281 Lines 4832 3596 -1236 ========================================== - Hits 4066 2791 -1275 - Misses 766 805 +39 ``` | [Impacted Files](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab) | Coverage Δ | | |---|---|---| | [src/tests/schema\_validation/v2\_0\_1.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3Rlc3RzL3NjaGVtYV92YWxpZGF0aW9uL3YyXzBfMS5ycw==) | `77.26% <ø> (-7.15%)` | :arrow_down: | | [src/v1\_6/types/authorization\_data.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3YxXzYvdHlwZXMvYXV0aG9yaXphdGlvbl9kYXRhLnJz) | `0.00% <0.00%> (ø)` | | | [src/v1\_6/types/charging\_schedule\_period.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3YxXzYvdHlwZXMvY2hhcmdpbmdfc2NoZWR1bGVfcGVyaW9kLnJz) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [src/v1\_6/types/key\_value.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3YxXzYvdHlwZXMva2V5X3ZhbHVlLnJz) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [src/v1\_6/types/location.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3YxXzYvdHlwZXMvbG9jYXRpb24ucnM=) | `0.00% <0.00%> (ø)` | | | [src/v1\_6/types/measurand.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3YxXzYvdHlwZXMvbWVhc3VyYW5kLnJz) | `0.00% <0.00%> (ø)` | | | [src/v1\_6/types/meter\_value.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3YxXzYvdHlwZXMvbWV0ZXJfdmFsdWUucnM=) | `0.00% <0.00%> (-100.00%)` | :arrow_down: | | [src/v1\_6/types/phase.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3YxXzYvdHlwZXMvcGhhc2UucnM=) | `0.00% <0.00%> (ø)` | | | [src/v1\_6/types/reading\_context.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3YxXzYvdHlwZXMvcmVhZGluZ19jb250ZXh0LnJz) | `0.00% <0.00%> (ø)` | | | [src/v1\_6/types/reason.rs](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab#diff-c3JjL3YxXzYvdHlwZXMvcmVhc29uLnJz) | `0.00% <0.00%> (ø)` | | | ... and [270 more](https://codecov.io/gh/codelabsab/rust-ocpp/pull/13/diff?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab) | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=codelabsab)

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[tommymalmqvist]

Thank you for the PR @larsk2009

I think we should drop #30848bc since using full nested structs is more extensive.

Also, nice find with #4594806

[larsk2009]

Okay, I'll remove that commit