ZEVA2 - vehicle models

**Describe the task**
Implement the models associated with vehicles in schema.prisma (e.g. vehicles, vehicle_history, vehicle_comments, etc.)

**Purpose**
This is necessary for users to save vehicles and associated objects to the database.

**Acceptance Criteria**
- [ ] The models are created, using/creating enums where necessary (e.g. the model_year field, the zev_type field, etc. of the vehicles table in zeva1).
- [ ] The seed.ts file is updated to bring over the zeva1 vehicle-related records to zeva2.