Extend vehicle API endpoints to support all editable fields #1280

[iamdabe]

This PR extend the existing Vehicles endpoint to include all editable fields bringing the API’s functionality in line with the UI as discussed in issue #1280

The primary goal was to support adding and editing Purchase and Sold information via the API. While I was there it wasn't much effort to add the other missing fields too.

Add/Update Vehicle (POST /api/vehicle/add, PUT /api/vehicle/update)

• Added support for ImageLocation, PurchaseDate, SoldDate, PurchasePrice, SoldPrice, OdometerMultiplier, and OdometerDifference fields on the VehicleInputModel
• Added pre-flight validation for date-parseable strings (PurchaseDate, SoldDate), decimal (OdometerMultiplier), and integer (OdometerDifference) fields before attempting to apply them
• Add endpoint applies safe defaults (OdometerMultiplier = "1", OdometerDifference = "0", HasOdometerAdjustment = false) when fields are omitted. Update endpoint skips fields not provided for backwards compatibility.
• I've also included the IsElectric and IsDiesel patch that resolves bug changing fuel type.

Image Upload (POST /api/images/upload)

• New endpoint for uploading vehicle images via the API
• Validates Content-Type starts with image/
• Rejects files larger than 500KB with a descriptive error (as no way to get width/height without including a 3rd party image package.
• Returns Location and Name on success, matching the existing UploadedFiles response pattern as used by documents upload endpoint

Image Upload Flow

To set a vehicle image via the API, first upload the image, then pass the returned location into the vehicle add/update payload.

1. Upload the image

POST /api/images/upload

Multipart form upload with the file in the image field. Max 500KB.

Returns:

{
  "location": "/images/abc123.jpg",
  "name": "mycar.jpg"
}

2. Use the location in Add or Update Vehicle

POST /api/vehicles/add

{
  "year": 2019,
  "make": "Nissan",
  "model": "Altima",
  "identifier": "LicensePlate",
  "licensePlate": "HITNCURBS",
  "fuelType": "Gasoline",
  "imageLocation": "/images/abc123.jpg",
  "purchaseDate": "2019-01-01",
  "purchasePrice": 20000.00,
  "odometerMultiplier": "1.0",
  "odometerDifference": "0"
}

PUT /api/vehicles/update

{
  "id": 1,
  "year": 2019,
  "make": "Nissan",
  "model": "Altima",
  "identifier": "LicensePlate",
  "licensePlate": "HITNCURBS",
  "fuelType": "Gasoline",
  "imageLocation": "/images/abc123.jpg",
  "soldDate": "2023-06-15",
  "soldPrice": 15000.00
}

Notes

• purchaseDate / soldDate — ISO 8601 date strings, optional
• purchasePrice / soldPrice — decimal, optional
• odometerMultiplier / odometerDifference — if either is provided, odometer adjustment is automatically enabled on the vehicle
• All fields except the required vehicle identifiers are optional on update (patch behaviour)