Fix: Make `VehicleReponseModel` values optional

[CM000n]

Interestingly, there are probably vehicles / accounts where the endpoints did not even return basic information to the car. See https://github.com/DurgNomis-drol/ha_toyota/issues/211

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (2c133e0) 70.50% compared to head (4cc1458) 70.50%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #307 +/- ## ======================================= Coverage 70.50% 70.50% ======================================= Files 30 30 Lines 1434 1434 ======================================= Hits 1011 1011 Misses 423 423 ``` | [Flag](https://app.codecov.io/gh/DurgNomis-drol/mytoyota/pull/307/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Simon+Hansen) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/DurgNomis-drol/mytoyota/pull/307/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Simon+Hansen) | `70.50% <100.00%> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Simon+Hansen#carryforward-flags-in-the-pull-request-comment) to find out more.

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[CM000n]

Thx for the approval. I will wait with the merge till I get some more info from the User in the corresponding issue

[CM000n]

I am closing this because the error is not on our side. The cause was probably a faulty/incomplete migration of the user vehicle to the new API: https://github.com/DurgNomis-drol/ha_toyota/issues/211#issuecomment-1899189236